File Revision Dale: 7 July 2019 ‘CBSE Objective Questions Exam 2019-2020, LASS: f0th SUB: Science For 15 Years Exams Chaplets Question Bank st www.ebse.online or uha'sapp at 8905629969 CHAPTER 13 Magnetice Effect of Electric Current 1. OBJECTIVE QUESTIONS 1 Instrument can be shielded from outside magnetic effects by surrounding them with (a) Rusbber shield (b) Glass shield (c) Iron shield (@) Brass shield Ans : (c) Iron shield 2. By removing the inducing maguet, the induced raguetism is (a) Finished after some time (b) Finished just after (6) Not finished for a long time (a) Not changed ‘Ans : (b) Finished just after 3. Choose the correct option (s). ‘The magnetic field inside a long straight solenoid. cazrying current (2) is zero. (b) decreases as we move towards its end. (C2) inerannen ws we rove toward its end (4) isthe same at all points Ans : (d) is te same at all points. NO NEED TO PURCHASE ANY BOOKS For session 2019-2020 free paf will be available at rwwr.cbse.online for 1, Previous 15 Years Exams Chapter-wise Question Bank }2. Previous Ten Years Exam Paper (Paper-wise). [3.20 Model Paper (All Solved). }4.NCERT Solutions All material will be solved and free pdf. Tt will be: provided by 30 September and will be updated regularly 4, Which of the following is not true (a) Induction precedes attraction (b) We cannot isolate a single pole (6) We ean maguetise an iron ring (4) A permanent magnet retains its magnetism even when heated on a fate Ans : (d) A permanent magnet retains its magnetistn ‘even when heated on a flame. Download all GUIDE and Sample Paper pdfs from www.cbse.online or www-rava.org.in 5, Which ofthe following correctly describes the magnetic field near a loug straight wire? (a) The field consists of straight lines perpendicular to the wire. (b) The field consists of straight lines parallel to the (c) The field consists of radial lines originating from ‘the wie. (4) The field consists of concentric circles centred on the wire. Ans : (dl) ‘Tho field consists of concentric circles ‘centred on the wire, © Magnetic field due to a current through a straight conductor depends on (@) current (b) distance from the wire {2 Both (a) and (b) (@) cross-sectional area of wire Ans :(c) Both (n) and (b) Magnetic feld due to a current through a straight conductor depends on the current and distance from the wire (r) Le. Bel ped ped 1h. "The manguetic Bold at a distance ¥ fom long wire carrying current [is 0.4. Tesla. The value of magnetic field at a distance 2r is (oat wort © 0167 @ir Ans : (a) 0.2 T &s, pod br hor Bod | b= B = 948 Soon 8 A positively-charged particle (alpie-particle) project- fed towards west is deflected Lowards north By a mage netic field. The direction of magnetic field is (a) towards south, (b) towards east (©) downward (2) upward ‘Ans : (d) upward 8. The magnetic lines of force, inside a current carrying Page 118Chap 13 : Maguetice Effect of Blectrie Current solenoid, are (a) along the axis and are parallel to each other (b) perpendicular ta the axis and equidistance from cach other (c) eireular and they do not interseet each other (4) circular at the onds but they are parallel to the axis inside the solenoid, ‘Ans : (a) along the axis and are parallel ta each other 10, Which of the following statement is not correct about two parallel conductors carrying equal currents in the same dizection? (a) Back of the conductors will repel eael other. (b) The two conductors will repel ench other. (€) The aro concentric lines of force around each conductor (a) Back of the conductors will move if not prevented from doing so ‘Ans : (b) The two conductors will repel each other MW. Force on a current carrying conductor in a magnetic field depends on (a) direction of the current (b) direction of magnetic field (©) Both (a) and (b) (4) length of the wire ‘Ans : (c) Both (a) and (b) ‘The direction of force on the conductor depends on 1. direction of current 2, direction of magnetic field Force on the conductor is maximum when the direction of current is at right angle to the direction of magnetic field, NO NEED TO PURCHASE ANY BOOKS For session 2019-2020 froe pa will be available at ewve-cbse.online for 1. Previous 15 Years Exams Chapter-wise Question Bank }2, Previous ‘Ten Years Exam Paper (Paper-wise), {3.20 Model Paper (All Solved). 4. NCERY Solutions All material will be solved and free pdf, Ib will be provided by 30 September and will be updated regulary. ‘Aniy mtd py seas Aww tole CONE sans Cony Bos 12 Which of the following processes will not produce new rnagnetie poles? (a) cutting & bar magnet in helt (}) turning on a current in a solenoid (c) runaing a curzeat through a straight wise (4) placing an ton rod in contact with & magnet Ans :(c) running a current through a straight wire WA tesla is equivalent to a (a) newton per eoulom (b) newton per ampere-meter Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in " wo cbse.online (©) ampore per newton (a) newton per ampere-second Ans: (b) newton per amperemeter ‘To avoid risk of electrical shock, which phenomena is used? (a) Over londing (c) Barthing ‘Ans + (c) Earthing ‘To avoid risk of eleettical shock, the metal body of appliance is earthed, Earthing means to connect the metal ease of the appliance to earth by means of a metal wiee called earth wire, One end of the metal wire is buried in the earth, (b) Short circuiting, (a) None of these A ship is to reach a place 8° south of west, In what direction should the ship be stecred if declination at the place is 18° west? (a) West of magnetic south at angle 64° (b) Bast of magnetic north at angle 64° (6) West of magnetic south at angle 50° (2) Bast of may Ans : (a) West of magnetic south at angle 64° As the ship Is co reach a place 8° South of West, ice, along OA, as shown in figure, o, the ship should be steered West of maguetie North at an angle of (90° ~ 18" — 8") — 64" wtie north al angle 18° Geographic Magnetin, . North North Geographic Geographic North East "Magnetic Geographic South South, ‘The effective length of the magnet is (a) the complete length ofthe magnet (0) the distance between the two poles of the magnet {o) the half ofthe length of the magnet (4) the square of the length ofthe magnet Ans : (b) the distance between the two poles of the magnet A small magnet is placed perpendicular to a uniform 1magner field. ‘The forees acting on the magnet will result in (@) Rotational motion (b) Translatory motion (6) No motion at all (@) Translational and rotational motion both Ans : (a) Rotational motion Page 119Chap 13: Magnetice Effect of Blectrie Current 18, ‘The maguolie field at point due to a current carrying conductor is directly proportional to the (a) current flowing through to the (b) Distance feom the conductor (6) Voltage across the conductor (4) Resistance of the conductor ‘Ans : (a) current flowing through to the 19. A rectangular loop carrying a current i is situated near a long straight wire such that the wire is parallel to one of the sides of the loop and isin the plane of the loop. Ifa steady current i is created in wire as shown in figure below, then the loop will Wy (a) rotate about an axis parallel to the wire (b) move towards the wire (©) move away from the wire or towards right (a) remain stationary ‘Ans : (b) move towards the wire As, nen So, RB Fn =A B directed towards the wite Bio = Fy T A D heb 2%. Which of the following determines the direction of magnet field due to 8 current carrying conductor? (a) Faraday’s laws of electromagnetic induction (b) Floming’s left-hand rule (6) Lou's rule (@) Maxwell's cork serew-rale ‘Ans : (d) Maxwell's cork serew-rule 2L_ Magnetic lines do uot intersect on one-another because (a) they are at a distance (b) they are in the same direction (€) they are parallel to another (4) at the point intersection there will be wo direction ‘of the maguetie force whiel is impossible Download all GUIDE and Sample Paper pdfs from www.cbse.online or www-rava.org.in ‘Ans : (d) at the point intersection there will be Lye direction of the magnetic force whieh is impossible 22, A vertical wire carries a current upward. The magnetic field north of the wire will be dircetod (a) upward (b) eastward (0) westward (@) northward Ams : (6) westward 28, When the bars of bismuth are placed betwen the magnetic poles they set their length (a) perpendicular to the lines of force {B) along the Tne of force (©) neither perpendiculae nor along the lines of force (d) In any direction ‘Ans: (e) perpendicular tothe lines of force 2%, Which one of the following substances is the magnetic substances? (a) Mercury (b) Iron (©) Gold (@) Silver ‘Ans : (b) Iron 2%. Four metal rods are placed, in turn, inside a coll of copper wire Direction of current | — LAA in eoil Metal rod Pp Paper clips ‘The table below gives the results of the experiment. Which rod would be the most suitable to use for the cease of a coil in a cirenit breaker? ‘Metal Number of paper rod clips picket up when ‘there is a current in ‘Number of paper clips still attracted, ‘when the current the coil is switched off. (a) 1 0 {b) 20 2 35 0 ia) 35 30 Ans : (¢) ‘The core of the circuit breaker should be made up of soft iron type magnetic material which can be strongly magnetisod. But it retains the magnetism till the current is flowing, Only in the option (c), itis correctly listed. As, it attracts the greatest member of clips when current is Page 120Chap 13: Magnotice Effect of Blectrie Current in the eoil and as soon as current is removed, it docs not attract any clips 28, A copper wite is held between the poles of a magnet. Magnet Wire ‘The current in the wire can be reversed. The pole of the magnet can also be changed over. In how many of the four directions shown can the force act on the (a (b) 2 (3 4 ‘Ans : (b) 2 From Fleming's left hand rule, we know that the Jorce acting on the wite must be perpendicular to the ccarrent in Lhe wire and the magnet field ‘This means, these are only two possibilities for ‘the direction of the force ie., upward or downward. ZL A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. ‘The current as seen from points A and B (in the plane ‘of paper and on the axis of the coil) is anti clockwise and clockwise respectively. ‘The magnetic field lines point from B to A. The N-pole ofthe resultant magnet is om the face close to fa) A (b) B (c) A if the current is stall, and B if the eurrent is large (4) B if the current is small and A if the current is large al \p Variable resistance “ie “GCy—t- K ‘Ans : (a) A ‘Three plotting compasses are placed close to a solenoid carrying a current. How many of the compass needles will change direction, if the current through the solenoid is increased? (Ignore the effect of the ‘earth's magnetic field). (a) Only 1 compass needle (b) 2 compass needle Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in wor cbse.online 3 compass needle (d) None of the above (a) None of the above ‘The plotting compass gives the direction of the ‘magnetic field. The magnitude of the current affects the strength of field and not the direction of the ‘magnetic field. So, the compass needles will not change the direction, NO NEED TO PURCHASE ANY BOOKS For session 2019-2020 free paf will be available at wwe.cbse.online for 1. Provious 15 Years Exams Chapter-wise Question| Bank }2. Previous ‘Ten Years Bxam Paper (Paper-wise). 20 Model Paper (All Solved) 4. NCERT Solutions All material will be solved and free pdf. Ié will be provided by 30 September and wil be update regularly 28, ‘The magnetic lines of force, inside a current carrying solenoid, are {a) along the axis and are parallel to each other (5) perpendicalar to the axis and equidistance from each other (e) circular and they do not intersect each other {@) cizeular at the ends but they are parallel to the axis inside the solenoid. (a) along the axis and are parallel to each other 2. FILL IN THE BLANK 1. A compass needle is a ‘Ans : Small ‘magnet. 2. Field lines are used to represent a As Magnetic field A Field lines are shown closer together where the magnetic field is ‘Ans : Greater 4A metallic wire carrying an electrie current has ‘associated with it a ele. ‘Ans : Magnetic § ‘The force that # magnetic field exerts on a current is always perpendicular to the ... and to the Ans : Field, Current & In @ magnetic field pointing away from you, an electron traveling to the right will experience a force fn the vas ditection. Ans : Downward Page 121Chap 13: Magnetice Effect of Blectrie Current 1. Magnetic filds are produced by ‘Ans : Currents, 8, Closeness of field lines indicate strength. ‘Ans : high magnetic field 4. Magnetic field lines emerge from the solenoid or a permanent magnet, Ans : North pole of a MW. Field lines come out of pole. Ans : North, South pole while enters from Mh The Nepole of a compass points to the pole of 1 permanent magnet. Ans :$ 1% In right hand thumb rule the thumb poiuts in the irection of ‘Ans : current W. You are looking into a solenoid, at its S-pole, along its axis. From your view point, the direction of the ‘current in the solenoid is ‘Ans lockwise M._Crowding the wires of a solenoid more closely together will ‘the strength of the fleld inside it. [Ans : Increase WS. A Permanent behaves like a solenoid because both contain currents in the form of Ans : Circles W8. ‘The field lines about the wire consist of a series of concentric circles whose direction is given by the vale Ans : Right-hand TM. Anclectric current can be used for making temporary ‘magnets known as ‘Ans : Blectromagnets 18, ‘The unit of magnetie field is ‘Ans : Tesla 18, ‘The $.1. unit of magnetic fu Ans : Weber 20. ‘The force between currents is called the force. ‘Ans : Magnetic DL The unit of seleinductance in $i “Ans : Henry system is 2, No force acts on a current carrying conductor when it wow cbse.online is to the magnetic field, ‘Ans : parallel |. The magnetic lines of force are the lines drawn in a magnetic field along which a Ans : North magnetic pole would move. ‘An em. is induced in a coil when it changes. ‘Ans : The magnetic fix linked with, In an AC generator, maximum number of lines of force pass through the coil when the angle between the plane of coil and lines of force is Ams : 90 ‘You are looking down the axis of a solenoid, and the current from your position is clockwise. The end of the solenoid facing you Is & a.m pole Ans : South 1. Red colour insulation is used for... wire. Ans : live A generator converts mechanical energy into ‘energy. It works on the basis of ‘Ans : Electrical, Electromagnetic induction Larger the number of turns in the solenoid, greater will be the ..... produced, ‘Ans : magnetic field In our houses we receive AC electric power of with a frequency of ‘Ans : 220V, 50 Th. An electromagnet is 8 magnet. ‘Ans : temporary . The frequency for A.C. (allernating current) in USA, [Ans : 60 He "The armature in a motor rotates within a...» fel, Ans : Magnetic ‘To produce DO, the output of a generator must be fed ‘through a Ans : Commutator In any generator, the current in the armature is of the Aype. Ans: A.C ‘The phenomenon of production of back emf in a coil due to flow of varying current through itis ealled ilindwetion, Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in Page 122Chap 13 : Maguetice Etfect of Blectrie Current BI. SL unit of magnetic field strength is ‘Ans : tesla » TRUE/FALSE LL The induced emf. depends only the turns of the col Ans : False 2. The magnitude of induced current ean be increased by decreasing the speed of rotation of coil Ans : False 8, It is standard practice to connect fuse wite in the noutral wire of the household wiving, ‘Ans : False 4. The magnitude of induced current can be decreased by Increasing the area of cross, section of coil, ‘Ans : False 5A positive charge projected along the axis of a current carrying solenoid moves undevinted from its original path, Ans : True 6 ergy associated with an clectrie fold is analogous to potential energy whereas the energy associated ‘with the magnetic field is analogous to kinetic energy. Ans : True 1. No not foreo acts on a rectangular coil carrying a steady current. when suspended freely in a uniform magnetic field. Ans : True 4. Anclectron and a proton move in a uniform magnetic ficld with same speed perpendicular to the magnetic field. They experience forces in opposite directions Jiffering, by a factor of 1840. ‘Ans : False {There is no change in the energy of a charged particle moving in a magnetic field although a magnetic force is acting on it Ans : False W. An clectron does not suffer any deflections while passing through a region. This makes sure that there js no magnetic field in that region. Ans : True TL We can use either a two pin (plug and socked) or a throe pin (plug and socket) while working with an lectric iron: Ans : False 1, The field at the centre of a long circular coil carrying Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in wr cbse.online current will be parallel straight lines, ‘Ans : True YA A magnetic field exists in the region surrounding ‘a magnet, in which the foroe of the magnet can be detected, Ans : True M_ Fleming's left hand rule helps us to find the direction ‘of the induced current. ‘Ans : False 16. The pattern of the magnetic field around a conductor due to an electric current flowing through it depends con the shape of the conductor. Ans : True 16. We use the ‘right hand thumb rule’ for finding the direction of the magnotie field due to both a (current carrying) straight wire as well asa citeular coil, Ans : Truc TA current-carrying conductor when placed in a ‘magnetic field always experiences a force. Ans : False M&_ The electrician must always follow the correct colour code while wiring the household circuits ‘Ans : True 18, ‘The direction of force on a current carrying conductor placed ina magnetic field ean be reversed by reversing the direction of current flowing in the conductor. Ans: True 20, While replacing a use wire’. the electrician must use 1 fuse wire of correct rating. ‘Ans : True 2L_ The direction of force on a current carrying conductor placed in a magnetic field cannot be reversing the direction of magnetie Held, ‘Ans : False 2, Every household cixenit must have proper earth wire installed init Ans : True 28. Two magnetic lines of force newer intersect each other. Ans : True 2A. Its always good habit not to touch an electric switel with wet hands. ‘Aus : True 2%, ‘The field lines inside the infinite solenoid are in the form of parallel straight lines. ‘Ans : True 2%. An electric generator works on the principle of Page 123Chap 13 : Maguetice Etfect of Electric Current lectromagnetic induction, Ans : True 2, Ina DC electric motor @ pair of split rings Is used as commutator. Ans : True 4. MATCHING QUESTIONS DIRECTION : Each question contains statements given in itched. Statements (A, B,C, with statements (p,q, 3) ‘ovo columns which have to be x D) in column I have to be m in column 1 1 Column 1 Cohnmn TT 4 wr cbse.online Column T Column 1 (B) | Magnetic field in second quadrant {q)_ outwards (©) [Magnetic field in [fey | may be third quadrant inwards of (D) | Magnetic field in fourth quacirant Act, Bea, C- Ans Dp In column J, the position of small current carrying loops have been shown and in column II information related to force experienced by coil is given. Matel the entries of column T with the entries of column TL(Assume solenoid radius to be small as compared to its length) (A) [Anclectric | () motor works to a battery (B) ]Anelectric [(q)_Jairect current motor is also (© [Acommute- |G) tor is used to (D) [Commute] (s) tor rings are reverse the ditection of flow of eurzent known as DC MO- TOR connected Column 1 (p) J Auractve Column 1 (a) (a) | Repulsive Ans + Acq, Bes, Cor, Dep 2. Column TI gives approximate values of magnetic fields due to source given in column T (A) [At surface of neutron | (p) [100° zero, then (B) [Near big electromag- | (q) [1.57 crass Ans: At, Ba, C-s, D-p (b) [pa t 5 r 4. qual si fle ra id oe 2 2 - mie sicatis tame eens [ig Te Jae Ie Te Imray ens Column 1 ‘Column IL (A) PMagnetie Held in [(p) inwards first quadrant Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in ‘The force experienced by a coil in a magnetic field is sven by p, 5B P= PB Where, $2 is the increment of B along magnetic dipole ‘tnoment of contour, You can write the expression for magnetic field due to solenoid at a general point and ‘then differentiate it, From this information, you can have the results, Whether the force is attractive or repulsive can also be found by using the concept of nature of poles induced on the solenoid and evi Page 124Chap 13 : Maguetice Effect of Blectrie Current The force comes oul to be zero al contre and as wwe approach it from some outside point, its value For D: The coll first rotates to align itself in such f manner so as to link maximum flux and then the ‘ease would be sate as that of C. 5, In magnetic field, for @ charged particle, match the ‘entries of column I with the entries of column Il Column t Column TT (A) [Acceleration (0) [may be zero (B)_[Welocity (a) [is zero (© [Speed (©)_| may be constant (D)_[inotic energy _[és) is constant a B ce D @ |p * : = ws P 4 * pas ne @ @fas [ar Is * Ans: (a) A-p, Ber, C-s,-D-s Work done by magnetic force is zero. From work- ‘energy theorem, its speed or kinetic energy is constant ‘Two wires each carrying a steady current I are shown in four configurations in Column 1. Some of the resulting effects are described in Column Il. Mate the statements in Column I with the statements in ccolan H Column 1 Column 1 (A) [Point P is situated mich [(p) | The way between the wires, — fields (B) at Pe P due to the ceurrents in the wires are im the same direction. (B) [Point P is situated at | (a) | The mag- the mid-point of the line netie fields Joining the centers of the B) a P ‘ireular wires, which have | | due to the same radii currents in p the wires are , : in opposite POY directions. (© [Point P is situated at [(2) | There is no the mid-point of the line joining the centers of the sagnetic field at P. ‘circular wires, which have \e S wr cbse.online Colum T ‘Colinas (D) [Point P is situated at the fe) [The wices common center of the repel each =~ other ©) A B c D ] (a) [pr ne a8 3 | es b 4 r | © far |p ar | @ [avs @ 8 | ‘Aus: (6) Aca, Bp, C-a, #, D-a,8 ‘Tho magnetic field at P duc to eurrent flowing in AB is perpendicular to the plane of paper acting vertically downward, And the magnetic field at P duc to current flowing in CD is perpendicular to the plane of paper acting vertically upwards ‘Therefore, q is correct [As P is the mid point, the two magnetic fields, cancel ‘out each other. Therefore, r is correct Bp ‘The magnetic field at P due to current in loop A is along the axial line towards right. Similarly, the ‘magnetic field at P due to current in loop B is also along the axial line towards right. Ca, r ‘The magnetic field due to current in loop A at P is equal and opposite to the magnetic field due to current in loop B at P. Digs ‘The direction of magnetic field at P due to eurrent in lop A is perpendicular to the plane of paper directed vertically upwards. The ditection of magnetic Field at P due to current in loop B is perpendicular to the plane of paper directed vertically downward, Since the current are in opposite direction the wires repel each other Column I contains some features of AC supply in India and Column I contains their relevant values/ details. Matel Coluzans 1 and I. ‘Column 1 Column 1 (A) | Average xms) potential |p) [100 differences (in volts) between the live wire ‘household in India. (B) | Value of the frequency |(a) | 220 of AC supply in India. (©) | Namber of times the — |(0) [Green (yellow) household supply. voltage attain its peak Download all GUIDE and Sample Paper pd from www-cbse.online or www.rava.org.in Page 125Chap 13 : Maguetice Elfect of Blectrie Current (D) | Colour of the earth wire |) [oo in household wiring. (&) | (Average rms) potential difference (in volts) between the neutral wire and the ground wire in a domestic electric circuits, Ans: A-g, BAL, Cp, Der, Bs 5. ASSERTION AND REASON DIRECTION : In the following questions, « statement of ssscrton (A) is followed by a statement of reason (BR). Marke the correct choice a8 () Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (a). (b) Both assortion (A) and reason (R) axe true but reason (R) Js not the correct explanation of assertion (A). (6) Assertion (A) is true but reason (R) is false (4) Assertion (A) is false but reason (R) is true. (6) Both Assertion and Reason are fale L Assertion : Safety fuses are made up of materials having a low melting point: Reason : Safety fases should be resistant to electric ‘current. Ans : (c) Assertion (A) is true but reason (R) is false. 2 Ass On freely suspending a current - carrying solenoid, it comes to rest in N-S direction just like a bar magnet, Reason : One end of current carrying straight solenoid behaves as a North pole and the other end as a South pole, ‘Ans : (a) Both assertion (A) and reason (R) are true fand reason (R) is the correct explanation of assertion (a). 8, Assertion : Copper is used to make electric wires ‘Reason : Copper has very low clectrical resistance, ‘Ans : (a) Both assertion (A) and reason (R) are true tnd reason (R) is the correct explanation of assertion (A), ‘The low electrical resist ‘conductor for electricity ce of copper makes it a good 4. Assertion : A compass needle is placed near a current ‘carrying wire. The deflection of the compass needle decrenses when the magnitude of an electric current in the wire is increased. Reason : Strength of a magnetic field at a point near the conductor increases on increasing the current. ‘Ans : (d) Assertion (A) is false but reason (R) is true, 8. Assertion : AC load line is used for long distance Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in ry wr cbse.online transmission. Reason It has very less los of energy in long distance ‘transmission. ‘Ans : (a) Both assertion (A) and reason (R) are true ‘and reason (R) is the correct explanation of assertion (A), It can be easly transmitted over long distance without rch loss in energy. Assertion : When two bulbs are operated on same voltage supply, having power 60 W and 100 W then 100 W bulb bas less resistance than 60 W_ Reason : The power of the bulb is dizeetly proportional to the square of the voltage. Ans: (b) Both assertion (A) and reason (R) are ‘true but reason (R) is nat the correct explanation of assertion (A), Sine, poror(P) = or Red r Hence, 100 W bulb has less resistance. Assertion : ‘The magnitude of the magnetic field at ‘4 point on the axis of a current carrying solenoid is inversely proportional to the current lowing through the solenoid. Reason : The magnitude of the magnetic field at a point on the axis of a current carrying solenoid is directly proportional to the number of turns per unit length of a solenoid, ‘Ans : (d) Assertion (A) is false but reason (R) is true, Assertion An induced emf. appears in any coil in ‘whieh the curtent is changing [Reason : Self induction phenomenon obeys Faraday’ law of induction, Ans: (b) Both assertion (A) and reason (R)_are ‘rue but reason (R) is not the eorrect explanation of assertion (A) Assertion : The magnetic field produced by a current carrying solenoid is independent of its length and cross-section area, Reason : The sagt uniform, ‘Ans: (b) Both assertion (A) and reason (R) are true bul reason (R) is not the correct explanation of assertion (A) ficld inside the solenoid is ‘The magnetic field is independent of length and area, It is uniform inside the solenoid. Assertion : ‘The magnetic field is stronger at a point which is nearer to the conductor and goes on decreasing on moving away from the conductor Reason : The magnetic field B produced by a straight ccurzent carrying wize is inversely proportional to the distance from the wire Ans : (a) Both assertion (A) and reason (R) are true ‘and reason (R) is the correct explanation of assertion (a), Page 126Chap 19: Magnotice Effect of Blectrie Current snot field is ‘The magnitude of 1. ditectly proportional to the current J passing through the wire 2 Inversely proportional to the distance r from the ‘The magnetic field is stronger at a point which is nearer to the conductor and goes on decreasing on ‘moving away from the conductor. M1, Assertion : A solenoid tends to expand, when a current passes through it, Reason : Two straight parallel metallic wires carrying ‘current in same direction attraet each other. ‘Ans : (d) Assertion (A) is false but reason (R) is true. When current flows through a solenoid, the currents in the various turns of the solenoid are parallel and in ‘the same direction. Since the current flowing through parallel wires in the same direction lead to force of attraction between them, the turns of the solenoid will ‘also attract each other and as a result the solenoid tends to contract. 1 Assertion: A direction current flows through a metallic rod, produced magnetic field only outside the rod. Reason : There is no low of charge carriers inside the rod, Ans :(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A) Tn the case of metallic rod, the charge carries flow ‘through whole of the crostsection. Therefore, the magnetic field exists both inside as well as outside, However, magnetic field inside the rod will go no decreasing as we go towards the axis. 18. Assertion + Force experienced by moving charge ‘will be maximum if direction of velocity of charge is Perpendicular to applied magnetie fel Reason : Force on moving charge is independent of irection of applied magnetic field. ‘Ans : (c) Assertion (A) is true but reason (R) is false From equation = geBsin9. Force on moving charge will be maximum if direction of velocity of charge is perpendicular to direction of magnetic field (when = 90") Me Asse Electric appliances with metallie body hhave three connections, whereas an electric bulb has two pin connections. Reason : Three pin connections reduce heating of ‘connecting wires, ‘Ans :(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A), ‘The motallie body of the electrical appliance is ‘connected to the third pin which is connected to the earth. This is a safety precaution and avoids eventual clectrie shock. By doing, this the extra charge flowing through the metallic body is passed to earth and avoid shocks, ‘There is nothing such as reducing the heating ‘of connecting wires by three pin connections. 18. Assertion : There is no change in the energy of a wow cbse.online charged particle moving in a magnetic field although ‘a magnetic force is acting on it Reason : Work done by centripetal force is always Ans : (a) Both assertion (A) and reason (R) are true ‘and reason (R) is the correet explanation of assertion a. ‘Magnetic force is always perpendicular to the direction of motion of charged particle, Le., work done on the charge particle moving on a circular path in magnetic field zero. Assertion : When two long parallel wires, hanging freely are connected in series to a battery, they come closer to each other. Reason : Wires carrying current in opposite direction repel each other ‘Aus: (b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A). ‘The wires are parallel to each other but the direction of current in it is in same direction so they attract each other. If the current in the wire is in opposive direction then wires repel each other 1. Assertion : In a conductor, free electrons keep on wing but no magnetic force acts on a conductor in ‘a magnetic field Reason : Force on froe electrons due to magnetic fold always acts perpendicular to its direction of motion. ‘Ans : (c) Assertion (A) is true but reason (I) is false. In a conductor, the average velocity of electrons is zero, Hence no current flows through the conductor. Hence, no force acts on this conductor Assertion : A small coil carrying current, in cquilibrium, is perpendicular to the ditestion of the uniform magnetic field Reason : Torque is maximum whea plane of coil and digection of the magnetic field are parallel to cach other. ‘Ans: (b) Both assertion (A) and reason (R) are true but reason (2) is not the comet explanation of assertion (A), ‘The torque acting on a col is given by, 7 =NIA Dsind ‘where 0 is the angle betseeen the plane of the coil and the direction of magnetic field, When 9= 90", then 0. The coil tries to orient itself in this postion ‘Thus in equiibeium, the coil acquires a position, such that its plane makes an angle 90° with the direction of magnetic field. Assertion : A current carrying conductor experiences a force in a magnetic field, Reason ; The force acting on a current carrying conductor in a magnetic field is due to interaction between magnetic field produced by the current carrying conductor and external magnetic field in which the conductor is placed, ‘Ans: (b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in Page 127Chap 19: Magnetice Effect of Blectrie Current assertion (A). When a current carrying conductor is placed in a ‘magnetic field, it experiences « force except when itis placed parallel to the magnetic fleld. The force acting ‘on a current carrying conductor in a magnetic field is {due Lo interaction between magnetic field produced by the current carrying conductor and external magnetic field in which the conductor is placed. “Assertion : Basie difference between an electric Hine and magnetic line of force is tat former is discontinuous and the later is continuous oF endless. Reason : No electric lines of force exist inside a charged body but magnetic lines do exist inside a magnet. ‘Ans : (a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (a), In case of the electric field of an electric dipole, the lectrie lines of force originate from positive charge and, end at negative charge. Since, isolated magnetic lines are closed continuous loops extending throughout the body of magnet, hence they from endless curves. TL Assertion : On changing the direction of flow of carrent through a straight conductor, the direction ‘of a magnetic field around the conductor is reversed. Reason : The direction of magnetic field around a conductor ean be given in accordance with left hand ‘thumb rule, ‘Ans : (c) Assertion (A) is true but reason (R) is false. 2 Assertion : Two bar magnets attract when they are brought near to each other with the same pole, Reason : Unlike poles will attract each other. ‘Ans : (d) Assertion (A) is false but reason (R) is true, Assertion : Magnet field lines never intersect Reason : At a particular point magnetic field has only ‘one direction Ans : (a) Both assertion (A) and reason (R) are true tnd reason (R) is the correct explanation of assertion (a). 2%. Assertion : In Fleming's Left Hand Rule, the direction ‘of magnetic field, force and current are mutually perpendicular. Reason ; Fleming's Left hand Rule is applied to ‘measure the induced current. ‘Ans : (c) Assertion (A) is true but reason (R) is false It is used to find the direction of force in a current ‘carrying conductor in the presence of magnetic fel. Assertion : A compass needle is placed near a current ‘carrying wire. The deflection of the compass needle decreases when the compass needle is displaced away from the wire Reason : Strength of a magnetic field decreases as one moves away from a current carrying conductor ‘Ans : (3) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (a). Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in 30, Assertion wow cbse.online Asse No net force acts on a rectangular coil carrying a steady current when suspended freely in a uniform magnetic field. Reason : Force on coil in magnetic fold is always non ‘Ans : (¢) Assortion (A) is trne but reason (R) is fas. Force acting on each pair of the opposite sides of the coll are equal Assertion + an induced current has a direction such that the magnetic fux that induces the current, Reagon : Above statement is in accordance with ‘conservation of energy. Ans : (a) Both assertion (A) and reason (R) are true ‘and reason (R) is the correct explanation of assertion (A), + A proton moves horizontally towards a vertical long conductor having an upward electric current It will deflect vertically downward Reason : Seeing the proton and the conductor From the side of the proton, the magnetic field at the site of the proton will be towards right, Hence the force B= gx B wil defect the proton vertically downward ‘Ans : (a) Both assertion (A) and reason (R) are true ‘and reason (R) is the correct explanation of assertion (A), Assertion : Lonz’s law violates the principle of conservation of energy. Reason : Induced e.mf. always opposes the change in ‘magnetic flux responsible for its production. ‘Ans : (a) Both assertion (A) and reason (R) ate true ‘and reason (R) is the correct explanation of assertion . Lenz's law (that the direction of induced emf. is always such as to oppose the change that cause it) is direct consequence of the Inw of conservation of energy. Assertion : A nentral body may experience a net nom zero magnetic force. Reason : The net charge on a current carrying wire is ‘zero, but it can experience a force in a magnetic field ‘Ans : (a) Both assertion (A) and reason (R2) are true ‘and reason (R) is the correct explanation of assertion (a. Assertion : When number of turns in a coil is doubled coefficient of seltinductance of the coil becomes 4 times, Reason : This is because Le ‘Ans :(b) Both assertion (A) and reason (R) are ‘true but reason (R) is not the correct explanation of assertion (A), Assertion : Alternating Current is used in household supply. Reagon + AC electric power ean be transtaitted over long distance without much loss of energy. ‘Ans : (a) Both assertion (A) and reason (R) are true Page 128Chap 13 : Maguetice Effect of Blectrie Current fand reason (R) is the correct explanation of assertion (A), 3% Assertion : The strength of the magnetic field produced at the centre of a current carrying circular ‘oil increases on increasing the current flowing through the coil Reason: Magnetic field strength is inversely proportional to the eusrent flowing in the coil ‘Ans : (c) Assertion (A) is true but reason (R) is false, W. Assertion : ‘The strength of the magnetic field produced at the centre of a current caning cizcular col increases on increasing the radius of the circular Reason : Maguctie field strength is inversely proportional to the radius of the circular coil Ans :(d) Assertion (A) is flse but reason (R) is true 36 Assertion + ‘The strength of the magnetic feld produced atthe centre of current carrying ereular ‘il nerease on increasing the numberof taro ofthe cirealar col Reason: Magnetic fl strengths directly proportional to the number of tur ofthe etcular col ‘Ans: (a) Both assertion (A) and reason (R) are true tn reason (R) isthe correct explanation of exertion a) NO NEED TO PURCHASE ANY BOOKS {For session 2019-2020 free pdf will be available at wow.cbse.online for 1. Previous 15 Years Exams Chapter-wise Question Bank }2. Previous Ten Years Exam Paper (Paper-wise). 3. 20 Model Paper (All Solved). ]4. NCERT Solutions All material will be solved and free pdf, It will be provided by 30 September and wil be updated regularly sy maid pn tes Aco nn TE oy Bo sw cbse.online Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in Page 129