1. Resistance of a wire is yΩ. The wire is stretched to triple its length, then the resistance becomes ___________
a) y/3
b) 3y
c) 6y
d) y/6
Explanation: Resistance of a conductor is directly proportional to its length. That is, when the length of conductor is tripled, its resistance also gets tripled.
2. An electric current of 10 A is the same as ___________
a) 10 J/C
b) 10 V/C
c) 10C/sec
d) 10 W/sec
Explanation: Mathematically, electric current can be defined as the ratio of the charge to the time in which charge flows.
3. Consider a circuit with two unequal resistances in parallel, then ___________
a) large current flows in large resistor
b) current is same in both
c) potential difference across each is same
d) smaller resistance has smaller conductance
Explanation: In parallel combination of resistors, the potential difference across each resistors is the same.
4. In which of the following cases is Ohm’s law not applicable?
a) Electrolytes
b) Arc lamps
c) Insulators
d) Vacuum ratio values
Explanation: According to Ohm’s law, it is applicable only to conductors. Hence, Ohm’s law is not applicable in case of insulators.
5. A copper wire of length l and diameter d has potential difference V applied at its two ends. The drift velocity is V. If the diameter of wire is made d/4, then drift velocity becomes ___________
a) V/16
b) 16V
c) V
d) V/4
Explanation: Drift velocity is inversely propotional to area of material i.e, V=I/nAq.
6. Which of the following bulbs will have high resistance?
a) 220V, 60W
b) 220V,100W
c) 115V,60W
d) 115V,100 W
Explanation: Resistance is directly proportional to square of voltage and inversely proportional to the power.
7. Ohm’s law is not applicable to ___________
a) dc circuits
b) high currents
c) small resistors
d) semi-conductors
Explanation: Ohm’s law is not applicable to semi-conductors and insulators.
8. Conductance is expressed in terms of ___________
a) mho
b) mho/m
c) ohm/m
d) m/ohm
Explanation: Conductance is the reciprocal of resistance and is expressed in terms of mho.
9. Resistivity of a wire depends on ___________
a) length of wire
b) cross section area
c) material
d) all of the mentioned
Explanation: Resistivity of a wire is a constant and it depends on the type of material used.
10. In a current-voltage relationship graph of a linear resistor, the slope of the graph will indicate ___________
a) conductance
b) resistance
c) resistivity
d) a constant
Explanation: The slope of the graph is the ratio of current to a voltage which indicates conductance.