1. The specific resistance of all metals is most
affected by
a) Temperature
b) Pressure
c) Degree of illumination
d) Applied magnetic field
Explanation: With rise in temperature specific resistance increases
2.The positive temperature coefficient of resistance
is for
a) Carbon
b) Germanium
c) Copper
d) An electrolyte
Explanation: For metallic conductors, temperature coefficient of resistance is positive.
3.The fact that the conductance of some metals
rises to infinity at some temperature below a few
Kelvin is called
a) Thermal conductivity
b) Optical conductivity
c) Magnetic conductivity
d) Superconductivity
Explanation: Superconductivity
4. Dimensions of a block are \[1 cm \times 1 cm\times100 cm\] . If
specific resistance of its material is \[3 \times 10^{-7}ohm- m\] , then the resistance between the
opposite rectangular faces is
a) \[3 \times 10^{-9}ohm\]
b) \[3 \times 10^{-7}ohm\]
c) \[3 \times 10^{-5}ohm\]
d) \[3 \times 10^{-3}ohm\]
Explanation:
5. In the above question, the resistance between the
square faces is
a) \[3 \times 10^{-9}ohm\]
b) \[3 \times 10^{-7}ohm\]
c) \[3 \times 10^{-5}ohm\]
d) \[3 \times 10^{-3}ohm\]
Explanation:
6.There is a current of 20 amperes in a copper wire
of \[ 10^{-6}\] square metre area of cross-section. If the
number of free electrons per cubic metre is \[ 10^{29}\] ,
then the drift velocity is
a) \[125 \times 10^{-3}m / sec\]
b) \[12.5 \times 10^{-3}m / sec\]
c) \[1.25 \times 10^{-3}m / sec\]
d) \[1.25 \times 10^{-4}m / sec\]
Explanation:
7. The electric intensity E , current density j and
specific resistance k are related to each other by
the relation
a) \[E = j / k\]
b) \[E = jk\]
c) \[E = k / j\]
d) \[E = jE\]
Explanation:
8. The resistance of a wire of uniform diameter d
and length L is R . The resistance of another
wire of the same material but diameter 2d and
length 4L will be
a) 2R
b) R
c) R/2
d) R/4
Explanation:
9. There is a current of 1.344 amp in a copper wire
whose area of cross-section normal to the length
of the wire is \[1mm^{2}\] . If the number of free
electrons per \[cm^{3}\] is \[8.4\times 10^{22}\] , then the drift
velocity would be
a) 1.0 mm/sec
b) 1.0 m/sec
c) 0.1 mm/sec
d) 0.01 mm/sec
Explanation:
10.It is easier to start a car engine on a hot day than
on a cold day. This is because the internal
resistance of the car battery
a) Decreases with rise in temperature
b) Increases with rise in temperature
c) Decreases with a fall in temperature
d) Does not change with a change in temperature
Explanation:
