1. \[20\mu A\] current flows for 30 seconds in a wire,
transfer of charge will be
a) \[2\times 10^{-4}C\]
b) \[4\times 10^{-4}C\]
c) \[6\times 10^{-4}C\]
d) \[8\times 10^{-4}C\]
Explanation:
2. \[\sigma_{1}\] and \[\sigma_{2}\] are the electrical conductivities of Ge
and Na respectively. If these substances are
heated, then
a) Both \[\sigma_{1}\] and \[\sigma_{2}\] increase
b) \[\sigma_{1}\] increases and \[\sigma_{2}\] decreases
c) \[\sigma_{1}\] decreases and \[\sigma_{2}\] increases
d) Both \[\sigma_{1}\] and \[\sigma_{2}\] decrease
Explanation: Ge is semiconductor and Na is a metal. The conductivity of semiconductor increases and that of the metals decreases with the rise in temperature.
3. 1.6 mA current is flowing in conducting wire then
the number of electrons flowing per second is
a) \[ 10^{11}\]
b) \[ 10^{16}\]
c) \[ 10^{19}\]
d) \[ 10^{15}\]
Explanation:
4. A current I is passing through a wire having two
sections P and Q of uniform diameters d and d/2
respectively. If the mean drift velocity of
electrons in sections P and Q is denoted by vP and
vQ respectively, then
a) \[V_{P}=V_{Q}\]
b) \[V_{P}=\frac{1}{2}V_{Q}\]
c) \[V_{P}=\frac{1}{4}V_{Q}\]
d) \[V_{P}= 2V_{Q}\]
Explanation:
5. The resistance of a coil is 4.2 Ω at \[100^{\circ}C\] and the
temperature coefficient of resistance of its
material is \[0.004/^{\circ}C\] . Its resistance at \[0^{\circ}C\] is
a) 6.5Ω
b) 5Ω
c) 3 Ω
d) 4 Ω
Explanation:
6.Masses of three wires of copper are in the ratio of
1 : 3 : 5 and their lengths are in the ratio of 5 : 3 : 1. The ratio of their electrical resistances
are
a) 1 : 3 : 5
b) 5 : 3 : 1
c) 1 : 15 : 125
d) 125 : 15 : 1
Explanation:
7. Conductivity increases in the order of
a) Al, Ag, Cu
b) Al, Cu, Ag
c) Cu, Al, Ag
d)Ag, Cu, Al
Explanation: Al, Cu, Ag
8. The resistance of a conductor is 5 ohm at \[50^{\circ}C\] and
6 ohm at \[100^{\circ}C\] . Its resistance at \[0^{\circ}C\] is
a) 1 ohm
b) 2 ohm
c) 3 ohm
d) 4 ohm
Explanation:
9.If an electron revolves in the path of a circle of
radius of \[0.5\times 10^{-10}m\] at frequency of \[5\times 10^{15}\] cycles/s the electric current in the circle is (Charge
of an electron = \[1.6\times 10^{-19}C\] )
a) 0.4 mA
b) 0.8 mA
c) 1.2 mA
d) 1.6 mA
Explanation:
10.Equal potentials are applied on an iron and
copper wire of same length. In order to have the
same current flow in the two wires, the ratio r
(iron)/r (copper) of their radii must be (Given
that specific resistance of iron = \[1.0\times 10^{-7}ohm-m\]
and specific resistance of copper = \[1.7\times 10^{-8}ohm-m\] )
a) About 1.2
b) About 2.4
c) About 3.6
d) About 4.8
Explanation:
