MULTIPLE-CHOICE QUESTIONS
Q.1.When electric current is passed, electrons move from:
(a) high potential to low potential.
(b) low potential to high potential.
(c) in the direction of the current.
(d) against the direction of the current.
Q.2. The unit of resistivity is:
(a) V A
(b) V A
(c) V m /A
(d) VA/m
Q.3. What is the commercial unit of electrical energy?
(a) Joules
(b) Kilojoules
(c) Kilowatt-hour
(d) Watt-hour
Q.4. The instrument used for measuring electric current is :
(a) Ammeter
(b) Galvanometer
(c) Voltmeter
(d) Potentiometer
Q.5. Electrical resistivity of any given metallic wire
depends upon
(a) its thickness
(b) its shape
(c) nature of the material
(d) its length
Q.6. In an electrical circuit two resistors of 2 Ω and 4 Ω
respectively are connected in series to a 6 V battery. The
heat dissipated by the 4 Ω resistor in 5 s will be
(a) 5 J
(b) 10 J
(c) 20 J
(d) 30 J
Q.7. The heating element of an electric iron is made up of:
(a) copper
(b) nichrome
(c) aluminium
(d) iron
Q.8. Work of 14 J is done to move 2 C charge between two
points on a conducting wire. What is the potential
difference between the two points?
(a) 28 V
(b) 14 V
(c) 7 V
(d) 3.5 V
Q.9. While a cell is being charged, energy is converted into
energy.
a mechanical, electrical
b electrical, chemical
c heat, electrical
d chemical, heat
Q.10. The unit of potential difference is :
(a) Volt
(b) Ohm
(c) Ampere
(d) Faraday
Q.11. Copper is not preferred to make fuse wire because
it .
a is a good conductor of electricity
b has a low melting point
c has a high melting point
d is not easily available
Q.12. Coulomb is the SI unit of:
(a) Charge
(b) current
(c) potential difference
(d) resistance
ASSERTION-REASON TYPE QUESTIONS
Following questions consist of two statements – Assertion (A)
and Reason (R). Answer these questions selecting the
appropriate option given below:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of
A.
(c) A is true but R is false.
(d) A is false but R is true.
Q.1.. Assertion (A): When resistances are connected between
the same two points they are said to be in series.
Reason(R): When resistors are connected in series the current
through each resistor is the same.
Q.2. Assertion (A) : Tungsten metal is used for making
filaments of incandescent lamps.
Reason (R) : The melting point of tungsten is very low.
Q.3. Assertion (A): If a graph is plotted between potential
difference and current the graph is a straight line passing
through the origin.
Reason(R): current is directly proportional to the potential
difference.
Q.4. Assertion (A) : Longer wires have greater resistance and
the smaller wires have lesser resistance.
Reason (R) : Resistance is inversely proportional to the length
of the wire.-
Q.5. Assertion (A) : Alloys are commonly used in electrical
heating devices, like electrical iron, toasters etc.
Reason (R) : Alloys do not oxidise (burn) readily at high
temperatures.
6. Assertion (A) : Bending a wire does not affect electrical
resistance.
Reason (R) : Resistance of a wire is proportional to resistivity of
material.
Q.7. Assertion (A): A cell converts chemical energy into
electrical energy.
Reason(R): A cell maintains a potential difference across its
terminals due to chemical reactions.
CASE STUDY BASED QUESTION
Electrical resistivities of some substances at 20°C are given in
the table. Based on the info in the table, answer the given
questions.
Silver 1.60 X 10-8 m
Copper 1.62 X 10-8 m
Tungsten 5.2 X 10-8 m
Mercury 94 X 10-8 m
Iron 10 X 10-8 m
Nichrome 100 X 10-8 m
1 Which is a better conductor of electric current ?
(A) Silver (B) Copper (C) Tungsten (D) Mercury
2 Which element will be used for electrical transmission
lines ?
(A) Iron (B) Copper (C) Tungsten (D) mercury U
3 Nichrome is used in the heating elements of electric
heating device because:
(A) It has high resistivity
(B) It does not oxidise readily at high temperature
(C) Both of the above
(D) None of the above U
4 Series arrangement is not used for domestic circuits
because:
(A) Current drawn is less
(B) Current drawn is more
(C) Neither of the above
(D) Both of the above
TWO MARKS QUESTIONS
Q.1.Calculate the number of electrons that would flow per
second through the cross- section of a wire when 1 A current
flows in it.
Q.2. Define the following terms:
(a) one ampere (b) 1 volt.
Q.3. Keeping the potential difference constant, the resistance of
a circuit is doubled. By how much does the current change?
Q.4. How much work is done in moving a charge of magnitude
3 C across two points having a potential difference of 12 V?
Q.5. Define electric power. Write an expression relating electric
power, potential difference and resistance.
Q.6.Give reason for the following:
a Tungsten used almost exclusively for filament of electric
lamp.
b Why do we use copper and aluminium wires for
transmission of electric current?
Q.7. Distinguish between resistances in series and resistances
in parallel.
8. What is the better way of connecting lights and other
electrical appliances in domestic wiring? Why?
THREE MARKS QUESTIONS
Q.1. (a) List the factors on which the resistance of a conductor
in the shape of a wire depends.
(b) Why are metals good conductors of electricity whereas
glass is a bad conductor of electricity? Give reasons..
(c) Why are alloys commonly used in electrical heating
devices? Give reason.
2. A nichrome wire has a resistance of 10 Ω. Find the
resistance of another nichrome wire, whose length is three
times and area of cross-section four times the first wire.
Q.3. State the formula co-relating the electric current flowing in
a conductor and the voltage applied across it. Also, show this
relationship by drawing a graph. What would be the resistance
of a conductor, if the current flowing through it is 0.35 ampere
when the potential difference across it is 1.4 volt?
4.Calculate the total cost of running the following electrical
devices in April month if the rate of 1 unit of electricity is Rs.
6.00. (i) Electric heater of 1000 W for 5 hours daily. (ii) Electric
refrigerator of 400 W for 10 hours daily
5. (i) Consider a conductor of resistance ‘R’, length ‘L’,
thickness ‘d’ and resistivity ‘ρ’. Now this conductor is cut into
four equal parts. What will be the new resistivity of each of
these parts? Why?
(ii) Find the resistance if all of these parts are connected in:
(a) Parallel (b) Series
(iii) Out of the combinations of resistors mentioned above in the
previous part, for a given voltage which combination will
consume more power and why?
