1. An electron \[\left(charge=1.6\times 10^{-19}coulomb\right)\] is
moving in a circle of radius \[5.1\times 10^{-11}m\] at a
frequency of \[6.8\times 10^{15}\] revolutions/sec. The
equivalent current is approximately
a) \[5.1\times 10^{-3}amp\]
b) \[6.8\times 10^{-3}amp\]
c) \[1.1\times 10^{-3}amp\]
d) \[2.2\times 10^{-3}amp\]
Explanation:
2.A rod of a certain metal is 1.0 m long and 0.6 cm
in diameter. Its resistance is \[3.0\times 10^{-3}ohm\] .
Another disc made of the same metal is 2.0 cm in
diameter and 1.0 mm thick. What is the
resistance between the round faces of the disc
a) \[1.35\times 10^{-8}ohm\]
b) \[2.70\times 10^{-7}ohm\]
c) \[4.05\times 10^{-6}ohm\]
d) \[8.10\times 10^{-5}ohm\]
Explanation:
3.At what temperature will the resistance of a
copper wire become three times its value at 0oC
(Temperature coefficient of resistance for copper
= \[4\times 10^{-3}per^{\circ}C\] )
a) \[400^{\circ}C\]
b) \[450^{\circ}C\]
c) \[500^{\circ}C\]
d) \[550^{\circ}C\]
Explanation:
4. An electron revolves \[6\times 10^{15}times/sec\] in circular
loop. The current in the loop is
a) 0.96 mA
b) \[0.96 \mu A\]
c) 28.8 A
d) None of these
Explanation:
5. The charge of an electron is \[1.6\times 10^{-19}C\] . How
many electrons strike the screen of a cathode ray
tube each second when the beam current is 16 mA
a) \[ 10^{17}\]
b) \[ 10^{19}\]
c) \[ 10^{-19}\]
d) \[ 10^{-17}\]
Explanation:
6.If potential \[V=100\pm 0.5 volt\] and current
\[I=10\pm 0.2 amp\] are given to us. Then what will be
the value of resistance
a) \[10\pm 0.7\] ohm
b) \[5\pm 2\] ohm
c) \[0.1\pm 0.2\] ohm
d) None of these
Explanation:
7.A nichrome wire 50 cm long and one square
millimetre cross-section carries a current of 4A when connected to a 2V battery. The resistivity of
nichrome wire in ohm metre is
a) \[1\times 10^{-6}\]
b) \[4\times 10^{-7}\]
c) \[3\times 10^{-7}\]
d) \[2\times 10^{-7}\]
Explanation:
8. If an observer is moving with respect to a
stationary electron, then he observes
a) Only magnetic field
b) Only electric field
c) Both (a) and (b)
d) None of the above
Explanation: Both (a) and (b)
9. Calculate the amount of charge flowing in 2
minutes in a wire of resistance 10 Ω when a
potential difference of 20 V is applied between its
ends
a) 120 C
b) 240 C
c) 20 C
d) 4 C
Explanation:
10. If a wire of resistance R is melted and recasted to
half of its length, then the new resistance of the
wire will be
a) R/4
b) R/2
c) R
d) 2R
Explanation:
