SUCCESS STUDY CIRCLE

(a) Infinity (b) 1 

1. If a 0.1 % increase in length due to stretching, the
percentage increase in its resistance will be (c) 2  (d) 1.5 
(a) 0.2 % (b) 2 % 9. In the given figure, potential difference between A and
(c) 1 % (d) 0.1 % B is
2. The specific resistance of manganin is 50  10 8 ohm  m .
10K D
The resistance of a cube of length 50 cm will be (a) 0 A
30 V
6
(a) 10 ohm (b) 2.5  10 ohm5 (b) 5 volt 10K 10K
8 4
(c) 10 volt
(c) 10 ohm (d) 5  10 ohm
(d) 15 volt B
3. In hydrogen atom, the electron makes 6.6  10 15
10. The total current supplied to the circuit by the battery
revolutions per second around the nucleus in an orbit is
of radius 0.5  10 10 m . It is equivalent to a current
nearly (a) 1 A 2
6V 6
(a) 1 A (b) 1 mA (b) 2 A 3
(c) 1 A (d) 1.6  10 19 A 1.5
(c) 4 A
4. Two rods of same material and length have their (d) 6 A
electric resistance in ratio 1 : 2 . When both rods are
11. An electric current is passed through a circuit
dipped in water, the correct statement will be
containing two wires of the same material, connected
(a) A has more loss of weight in parallel. If the lengths and radii of the wires are in
(b) B has more loss of weight the ratio of 4/3 and 2/3, then the ratio of the currents
(c) Both have same loss of weight passing through the wire will be
(d) Loss of weight will be in the ratio 1 : 2 (a) 3 (b) 1/3
5. Masses of three wires of copper are in the ratio of 1 : 3 (c) 8/9 (d) 2
: 5 and their lengths are in the ratio of 5 : 3 : 1. The ratio 12. If a rod has resistance 4  and if rod is turned as half
of their electrical resistances are cycle then the resistance along diameter
(a) 1 : 3 : 5 (b) 5 : 3 : 1 (a) 1.56  (b) 2.44 
(c) 1 : 15 : 125 (d) 125 : 15 : 1 (c) 4  (d) 2 
6. If potential V  100  0.5 Volt and current I  10  0.2 13. If three resistors of resistance 2, 4 and 5  are
amp are given to us. Then what will be the value of connected in parallel then the total resistance of the
resistance combination will be
20 19
(a) 10  0.7 ohm (b) 5  2 ohm (a)  (b) 
19 20
(c) 0.1  0.2ohm (d) None of these 19 10
(c)  (d) 
7. Two resistors are connected (a) in series (b) in parallel. 10 19
The equivalent resistance in the two cases are 9 ohm 14. In circuit shown below, the resistances are given in
and 2 ohm respectively. Then the resistances of the ohms and the battery is assumed ideal with emf equal
component resistors are to 3 volt. The voltage across the resistance R4 is
50 
(a) 2 ohm and 7 ohm (b) 3 ohm and 6 ohm (a) 0.4 V
R1
+ R3 60  R4 30 
(c) 3 ohm and 9 ohm (d) 5 ohm and 4 ohm (b) 0.6 V 3V
– 50  R2
8. An infinite sequence of resistance is shown in the (c) 1.2 V R5 30 

figure. The resultant resistance between A and B will (d) 1.5 V

be, when R1  1 ohm and R 2  2 ohm 15. A parallel combination of two resistors, of 1  each, is
R1 R1 R1 R1 R1
A connected in series with a 1.5  resistor. The total
R2 R2 R2 R2 R2
combination is connected across a 10 V battery. The
current flowing in the circuit is
B
 (a) 5 A (b) 20 A amperes. The internal resistance of the cell is
(c) 0.2 A (d) 0.4 A
(a) 0.5 ohm (b) 1.0 ohm
16. If you are provided three resistances 2 , 3  and 6 .
(c) 1.5 ohm (d) 2.0 ohm
How will you connect them so as to obtain the
23. The terminal potential difference of a cell when short-
equivalent resistance of 4 
3 2 circuited is ( E = E.M.F. of the cell)
(a) E (b) E / 2
3 6
6 (c) Zero (d) E / 3
(a) (b) 24. A primary cell has an e.m.f. of 1.5 volts, when short-
2
circuited it gives a current of 3 amperes. The internal
resistance of the cell is
3
(a) 4.5 ohm (b) 2 ohm
2
(c) 6 (d) None of these (c) 0.5 ohm (d) 1/4.5 ohm
25. A 50V battery is connected across a 10 ohm resistor.
17. The figure below shows currents in a part of electric The current is 4.5 amperes. The internal resistance of
circuit. The current i is the battery i (a) Zero (b)0.5 ohm
(a) 1.7 amp 1amp (c) 1.1 ohm (d) 5.0 ohm
2amp
1.3amp 26. The potential difference in open circuit for a cell is 2.2
(b) 3.7 amp
volts. When a 4 ohm resistor is connected between its
(c) 1.3 amp 2amp two electrodes the potential difference becomes 2
(d) 1 amp i volts. The internal resistance of the cell will be
18. The terminal potential difference of a cell is greater (a) 1 ohm (b) 0.2 ohm
than its e.m.f. when it is (c) 2.5 ohm (d) 0.4 ohm
27. A new flashlight cell of e.m.f. 1.5 volts gives a current of
(a) Being discharged
15 amps, when connected directly to an ammeter of
(b) In open circuit resistance 0.04  . The internal resistance of cell is
(c) Being charged (a) 0.04  (b) 0.06 
(d) Being either charged or discharged (c) 0.10  (d) 10 
19. In the circuit shown, potential difference between X 28. A cell whose e.m.f. is 2 V and internal resistance is
and Y will be 40 X Y 0.1  , is connected with a resistance of 3.9  . The
(a) Zero voltage across the cell terminal will be
(b) 20 V (a) 0.50 V (b) 1.90 V
20 (c) 1.95 V (d) 2.00 V
(c) 60 V
120V
(d) 120 V 29. The reading of a high resistance voltmeter when a cell
is connected across it is 2.2 V. When the terminals of
20. In the above question, potential difference across the
the cell are also connected to a resistance of 5  the
40  resistance will be
voltmeter reading drops to 1.8 V. Find the internal
(a) Zero (b) 80 V
resistance of the cell
(c) 40 V (d) 120 V
(a) 1.2  (b) 1.3 
21. In the circuit shown, A and V are ideal ammeter and
(c) 1.1  (d) 1.4 
voltmeter respectively. Reading of the voltmeter will be
2V
30. When cells are connected in parallel, then
(a) The current decreases (b)The current increases
(a) 2 V
(c) The e.m.f. increases (d) The e.m.f. decreases
(b) 1 V A V
31. The internal resistance of a cell depends on
(c) 0.5 V
1 1 (a) The distance between the plates
(d) Zero
(b) The area of the plates immersed
22. When a resistance of 2ohm is connected across the
(c) The concentration of the electrolyte
terminals of a cell, the current is 0.5 amperes. When the
(d) All the above
resistance is increased to 5 ohm, the current is 0.25
32. n identical cells each of e.m.f. E and internal resistance 40. A dry cell has an e.m.f. of 1.5 V and an internal
r are connected in series. An external resistance R is resistance of 0.05  . The maximum current obtainable
connected in series to this combination. The current from this cell for a very short time interval is
through R is (a) 30 A (b) 300 A
nE nE (c) 3 A (d) 0.3 A
(a) (b)
R  nr nR  r
41. Consider the circuit given here with the following
E nE
(c) (d) parameters
R  nr Rr
E.M.F. of the cell = 12 V. Internal resistance of the cell
33. A cell of internal resistance r is connected to an
 2  . Resistance R  4 
external resistance R. The current will be maximum in E
R, if
(a) R  r (b) R  r
(c) R  r (d) R  r / 2 R
34. To get the maximum current from a parallel
combination of n identical cells each of internal Which one of the following statements in true
resistance r in an external resistance R, when (a) Rate of energy loss in the source is = 8 W
(a) R  r (b) R  r
(b) Rate of energy conversion in the source is 16 W
(c) R  r (d) None of these
(c) Power output in is = 8 W
35. Two identical cells send the same current in 2 
(d) Potential drop across R is = 16 V
resistance, whether connected in series or in parallel.
The internal resistance of the cell should be 42. A current of two amperes is flowing through a cell of
(a) 1  (b) 2  e.m.f. 5 volts and internal resistance 0.5 ohm from
negative to positive electrode. If the potential of
1
(c)  (d) 2.5  negative electrode is 10V, the potential of positive
2
36. The internal resistances of two cells shown are 0.1  electrode will be
(a) 5 V (b) 14 V
and 0.3  . If R  0.2  , the potential difference across
(c) 15 V (d) 16 V
the cell 2V, 0.1 2V, 0.3
43. 100 cells each of e.m.f. 5 V and internal resistance 1
A B ohm are to be arranged so as to produce maximum
(a) B will be zero
current in a 25 ohms resistance. Each row is to contain
(b) A will be zero
equal number of cells. The number of rows should be
(c) A and B will be 2V 0.2
(a) 2 (b) 4
(d) A will be  2V and B will be  2V (c) 5 (d) 10
37. A torch battery consisting of two cells of 1.45 volts and
44. The current in the arm CD of the circuit will be
an internal resistance 0.15  , each cell sending currents B
through the filament of the lamps having resistance
1.5ohms. The value of current will be (a) i1  i2 i2
i1
(a) 16.11 amp (b) 1.611 amp (b) i2  i3 O A
i3
(c) 0.1611 amp (d) 2.6 amp
(c) i1  i3
38. The electromotive force of a primary cell is 2 volts. C
When it is short-circuited it gives a current of 4 (d) i1  i2  i3 D
amperes. Its internal resistance in ohms is 45. When a resistance of 2 ohm is connected across the
(a) 0.5 (b) 5.0 terminals of a cell, the current is 0.5 A. When the
(c) 2.0 (d) 8.0 resistance is increased to 5 ohm, the current is 0.25 A.
39. The figure shows a network of currents. The magnitude The e.m.f. of the cell is
of currents is shown here. The current i will be (a) 1.0 V (b) 1.5 V
15A (c) 2.0 V (d) 2.5 V
3A
(a) 3 A 46. If six identical cells each having an e.m.f. of 6V are
8A
connected in parallel, the e.m.f. of the combination is
(b) 13 A (a) 1 V (b) 36 V
(c) 23 A 1
i (c) V (d) 6 V
6
(d) – 3 A 5A
47. Consider the circuit shown in the figure. The current I3 54. Four identical cells each having an electromotive force
is equal to 28 54 (e.m.f.) of 12V, are connected in parallel. The resultant
electromotive force (e.m.f.) of the combination is
(a) 5 amp
(a) 48 V (b) 12 V
(b) 3 amp 6V
(c) 4 V (d) 3 V
(c) 3 amp I3
55. Electromotive force is the force, which is able to
(d) 5 / 6 amp 8V 12 V maintain a constant
48. If VAB  4 V in the given figure, then resistance X will be (a) Current (b) Resistance
10 5V (c) Power (d) Potential difference
(a) 5  56. A cell of emf 6 V and resistance 0.5 ohm is short
A B circuited. The current in the cell is
(b) 10 
(a) 3 amp (b) 12 amp
(c) 15  2V X
(c) 24 amp (d) 6 amp
(d) 20 
57. A storage cell is charged by 5 amp D.C. for 18 hours. Its
49. Two resistances R 1 and R 2 are joined as shown in the strength after charging will be
figure to two batteries of e.m.f. E1 and E 2 . If E 2 is (a) 18 AH (b) 5 AH
short-circuited, the current through R 1 is
R1 (c) 90 AH (d) 15 AH
(a) E1 / R1
58. A battery having e.m.f. 5 V and internal resistance 0.5
(b) E 2 / R1
R2
 is connected with a resistance of 4.5  then the
E1 E2
(c) E 2 / R 2 voltage at the terminals of battery is
(a) 4.5 V (b) 4 V
(d) E1 /(R 2  R1 )
(c) 0 V (d) 2 V
50. A storage battery has e.m.f. 15 volts and internal
resistance 0.05 ohm. Its terminal voltage when it is 59. In the given circuit the current I1 is
delivering 10 ampere is 30 

(a) 30 volts (b) 1.00 volts (a) 0.4 A I1

40 
(c) 14.5 volts (d) 15.5 volts (b) – 0.4 A
I3
I2 40V
51. The number of dry cells, each of e.m.f. 1.5 volt and (c) 0.8 A 40 
internal resistance 0.5 ohm that must be joined in
(d) – 0.8 A 80V
series with a resistance of 20 ohm so as to send a
current of 0.6 ampere through the circuit is 60. The internal resistance of a cell of e.m.f. 12V is
(a) 2 (b) 8 5  10 2  . It is connected across an unknown
resistance. Voltage across the cell, when a current of 60
(c) 10 (d) 12
A is drawn from it, is
52. For driving a current of 2 A for 6 minutes in a circuit, (a) 15 V (b) 12 V
1000 J of work is to be done. The e.m.f. of the source
(c) 9 V (d) 6 V
in the circuit is
(a) 1.38 V (b) 1.68 V 61. The current in the given circuit is
10 
(c) 2.04 V (d) 3.10 V 5V

53. Two batteries of e.m.f. 4V and 8 V with internal

(a) 0.1 A A B
resistances 1  and 2  are connected in a circuit with
a resistance of 9  as shown in figure. The current and (b) 0.2 A
20 
potential difference between the points P and Q are (c) 0.3 A 2V
1 1 4V 8V 2 (d) 0.4 A
(a) A and 3 V
P Q
3
r1 r2 62. A current of 2.0 ampere passes through a cell of e.m.f.
1
(b) A and 4 V 1.5 volts having internal resistance of 0.15 ohm. The
6
1 9 potential difference measured, in volts, across both the
(c) A and 9 V ends of the cell will be
9
(a) 1.35 (b) 1.50
1
(d) A and 12 V (c) 1.00 (d) 1.20
2
63. A battery has e.m.f. 4 V and internal resistance r. When 70. In the above question, if the internal resistance of the
this battery is connected to an external resistance of 2 battery is 1 ohm, then what is the reading of ammeter
ohms, a current of 1 amp. flows in the circuit. How (a) 5/3 A (b) 40/29 A
much current will flow if the terminals of the battery (c) 10/9 A (d) 1 A
are connected directly
73. In an electrical cable there is a single wire of radius 9
(a) 1 amp (b) 2 amp
mm of copper. Its resistance is 5  . The cable is
(c) 4 amp (d) Infinite
replaced by 6 different insulated copper wires, the
64. Two batteries A and B each of e.m.f. 2 V are connected
radius of each wire is 3 mm . Now the total resistance of
in series to an external resistance R = 1 ohm. If the
internal resistance of battery A is 1.9 ohms and that of the cable will be
B is 0.9 ohm, what is the potential difference between (a) 7.5  (b) 45 
the terminals of battery A
(c) 90  (d) 270 
A B
74. Two uniform wires A and B are of the same metal and
(a) 2 V
have equal masses. The radius of wire A is twice that
(b) 3.8 V
of wire B . The total resistance of A and B when
(c) Zero R
connected in parallel is
(d) None of the above
(a) 4  when the resistance of wire A is 4.25 
65. When a resistor of 11  is connected in series with an
electric cell, the current flowing in it is 0.5 A. Instead, (b) 5  when the resistance of wire A is 4.25 
when a resistor of 5  is connected to the same (c) 4  when the resistance of wire B is 4.25 
electric cell in series, the current increases by 0.4 A.
(d) 4  when the resistance of wire B is 4.25 
The internal resistance of the cell is
75. Twelve wires of equal length and same cross-section
(a) 1.5  (b) 2  are connected in the form of a cube. If the resistance of
(c) 2.5  (d) 3.5  each of the wires is R , then the effective resistance
66. How much work is required to carry a 6 C charge from between the two diagonal ends would be
the negative terminal to the positive terminal of a 9 V
battery (a) 2 R
3 6
(a) 54 × 10 J (b) 54 × 10 J (b) 12 R
9 12
(c) 54 × 10 J (d) 54 × 10 J 5
(c) R
67. The emf of a battery is 2 V and its internal 6
resistance is 0.5 . The maximum power which it can (d) 8 R
deliver to any external circuit will be 76. You are given several identical resistances each of
value R  10  and each capable of carrying maximum
(a) 8 Watt (b) 4 Watt
current of 1 ampere. It is required to make a suitable
(c) 2 Watt (d) None of the above combination of these resistances to produce a
68. Kirchoff’s I law and II law of current, proves the resistance of 5  which can carry a current of 4
(a) Conservation of charge and energy amperes. The minimum number of resistances of the
(b) Conservation of current and energy type R that will be required for this job
(c) Conservation of mass and charge (a) 4 (b) 10
(d) None of these (c) 8 (d) 20
69. In the circuit, the reading of the ammeter is (assume 77. The resistance of a wire is 10 6  per metre. It is bend
internal resistance of the battery be zero) in the form of a circle of diameter 2 m . A wire of the
40
(a) A same material is connected across its diameter. The
29
10 A total resistance across its diameter AB will be
(b) A
9 4 10V
5 5
(c) A
3 A B
(d) 2 A
 (c) The 4 resistor is 0.50A (d)The 4 resistor is
0.25 A

(a) 4   10 6  (b) 2   10 6  82. There are three resistance coils of equal resistance. The
3 3
maximum number of resistances you can obtain by
(c) 0.88  10 6  (d) 14  10 6 
connecting them in any manner you choose, being free
78. In the figure shown, the capacity of the condenser C is
to use any number of the coils in any way is
2 F . The current in 2  resistor is
2 (a) 3 (b) 4
(c) 6 (d) 5
83. In the circuit shown, the value of each resistance is r,
3
2 F then equivalent resistance of circuit between points A
4
r
and B will be
+ –
6V 2.8 (a) (4/3) r
r r r
r
(b) 3r / 2
(a) 9 A (b) 0.9 A r r
(c) r / 3 A B
1 1 C
(c) A (d) A
9 0 .9 (d) 8r / 7
79. When the key K is pressed at time t  0 , which of the 84. If in the circuit shown below, the internal resistance of
following statements about the current I in the resistor the battery is 1.5  and VP and VQ are the potentials at
AB of the given circuit is true P and Q respectively, what is the potential difference
A B between the points P and Q
20 V 1.5 
2V K 1000 + –
1000

1 F C 3 P 2
(a) Zero
(b) 4 volts (VP > VQ)
2 Q 3
(c) 4 volts (VQ > VP)
(a) I = 2 mA at all t
(d) 2.5 volts (VQ > VP)
(b) I oscillates between 1 mA and 2mA
85. Two wires of resistance R1 and R2 have temperature
(c) I = 1 mA at all t
coefficient of resistance  1 and  2 , respectively. These
(d) At t = 0 , I = 2 mA and with time it goes to 1 mA
are joined in series. The effective temperature
80. A torch bulb rated as 4.5 W, 1.5 V is connected as coefficient of resistance is
shown in the figure. The e.m.f. of the cell needed to
1   2
make the bulb glow at full intensity is (a) (b)  1 2
4.5 W 2
1.5 V
 1 R1   2 R 2 R1 R 2 1 2
(c) (d)
(a) 4.5 V R1  R 2 R12  R 22
1
(b) 1.5 V
E(r=2.67)
86. Two cells of equal e.m.f. and of internal resistances r1
(c) 2.67 V and r2 (r1  r2 ) are connected in series. On connecting
(d) 13.5 V this combination to an external resistance R, it is
81. In the circuit shown in the figure, the current through observed that the potential difference across the first
3 2 2 cell becomes zero. The value of R will be
(a) r1  r2 (b) r1  r2
9V 8 8 4
r1  r2 r1  r2
(c) (d)
2 2
2 2 2
87. When connected across the terminals of a cell, a
(a) The 3 resistor is 0.50A (b)The 3 resistor is voltmeter measures 5V and a connected ammeter
0.25 A measures 10 A of current. A resistance of 2 ohms is
 connected across the terminals of the cell. The current (a) 6 A and 18 A
23 23
flowing through this resistance will be P
5 15
(a) 2.5 A (b) 2.0 A (b) A and A
26 26
3V
(c) 5.0 A (d) 7.5 A (c)
4
A and
12
A Q
1
25 25
88. In the circuit shown here, E1 = E2 = E3 = 2 V and R1 = R2 =
3 9
4 ohms. The current flowing between points A and B (d) A and A
25 25
through battery E2 is E1 R1
93. In the given circuit, it is observed that the current I is
(a) Zero independent of the value of the resistance R6. Then the
E2 resistance values must satisfy
(b) 2 amp from A to B A B
R5
(c) 2 amp from B to A E3 R2 I
(d) None of the above R1 R3
R6
(d) 1.0 A
R2 R4
89. A microammeter has a resistance of 100  and full
scale range of 50 A . It can be used as a voltmeter or as
a higher range ammeter provided a resistance is added (a) R1 R 2 R5  R 3 R 4 R6
1 1 1 1
to it. Pick the correct range and resistance combination (b)   
R5 R6 R1  R 2 R3  R4
(a) 50 V range with 10 k resistance in series
(c) R1 R4  R 2 R3
(b) 10 V range with 200 k resistance in series (d) R1 R3  R 2 R4  R5 R6
(c) 10 mA range with 1  resistance in parallel 94. In the given circuit, with steady current, the potential
(d) 10 mA range with 0.1  resistance in parallel drop across the capacitor must be
90. The potential difference across 8 ohm resistance is 48 (a) V V R

volt as shown in the figure. The value of potential (b) V / 2

V C
difference across X and Y points will be
(c) V / 3
X
3 2V 2R
(d) 2V / 3
(a) 160 volt
20 30 60 95. What is the equivalent resistance between the points A
(b) 128 volt
and B of the network
(c) 80 volt 24 8 48V 2 3
57 2
(a)  A
(d) 62 volt 1 7
Y 2
91. Two resistances R1 and R 2 are made of different (b) 8  4 1
10 1
materials. The temperature coefficient of the material (c) 6 
of R1 is  and of the material of R 2 is  . The 1.8
57 5
resistance of the series combination of R1 and R 2 will (d)  2.2
5
not change with temperature, if R1 / R2 equals B
96. The effective resistance between points P and Q of the
 
(a) (b) electrical circuit shown in the figure is
 

2  2 
(c) (d) 2R 2R
  (a) 2 Rr /(R  r)
92. A wire of resistance 10  is bent to form a circle. P and (b) 8 R (R  r) /(3 R  r) r 2R
r
Q are points on the circumference of the circle dividing
(c) 2r  4 R P Q
it into a quadrant and are connected to a Battery of 3 V 2R
and internal resistance 1  as shown in the figure. The (d) 5 R / 2  2r
2R 2R
currents in the two parts of the circle are 97. In the circuit element given here, if the potential at
point B, VB = 0, then the potentials of A and D are given
as
 103. Seven resistances are connected as shown in the figure.
1 amp 1.5  2.5  2V
The equivalent resistance between A and B is
10
A B C D
(a) 3 
A 10 3 B
(a) VA  1.5 V, VD  2 V (b) VA  1.5 V, VD  2 V (b) 4 
(c) VA  1.5 V, VD  0.5 V (d) VA  1.5 V, VD  0.5 V (c) 4.5  5 8 6 6
98. The equivalent resistance between the points P and Q (d) 5 
3
in the network given here is equal to (given r 
2 104. A battery of internal resistance 4 is connected to the
network of resistances as shown. In order to give the
1 r r maximum power to the network, the value of R (in  )
(a)  r
2 should be
r r
(b) 1  P Q (a) 4/9
R R
r
(c)
3
 r r
(b) 8/9 R 6R R
2 E
(c) 2
(d) 2  R 4R
(d) 18
99. The current in a conductor varies with time t as
I  2t  3t 2 where I is in ampere and t in seconds. 105. In the circuit shown here, the readings of the ammeter
Electric charge flowing through a section of the and voltmeter are
6 V, 1
conductor during t = 2 sec to t = 3 sec is
(a) 10 C (b) 24 C (a) 6 A, 60 V
V
(c) 33 C (d) 44 C 6 A
(b) 0.6 A, 6 V
100. A group of N cells whose emf varies directly with the (c) 6/11 A, 60/11 V 4
internal resistance as per the equation EN = 1.5 rN are
(d) 11/6 A, 11/60 V
connected as shown in the figure below. The current I
in the circuit is 106. Length of a hollow tube is 5m, it’s outer diameter is 10
1 cm and thickness of it’s wall is 5 mm. If resistivity of the
r1
2 material of the tube is 1.7  10–8 m then resistance
r2
(a) 0.51 amp of tube will be
N rN
(b) 5.1 amp r3
(a) 5.6  10–5  (b) 2  10–5 
3
(c) 0.15 amp r4
(c) 4  10–5  (d) None of these
(d) 1.5 amp 4
107. A wire of resistor R is bent into a circular ring of radius
101. In the shown arrangement of the experiment of the
r. Equivalent resistance between two points X and Y on
meter bridge if AC corresponding to null deflection of
its circumference, when angle XOY is , can be given by
galvanometer is x, what would be its value if the radius
R
of the wire AB is doubled (a) (2   )
4 2 X
R
(b) (2   )
(a) x 2 W  O Z
R1 R2
(b) x/4 (c) R (2 – )
G Y
(c) 4x 4
(d) (2   )
A R
(d) 2x x C B
108. Potential difference across the terminals of the battery
102. The resistance of a wire of iron is 10 ohms and temp. shown in figure is (r = internal resistance of battery)
coefficient of resistivity is 5  10 3 / C . At 20 C it carries
30 milliamperes of current. Keeping constant potential (a) 8 V 10 V r =1

difference between its ends, the temperature of the (b) 10 V

wire is raised to 120 C . The current in milliamperes
(c) 6 V 4
that flows in the wire is
(a) 20 (b) 15 (d) Zero
(c) 10 (d) 40