Class 12 Current Electricity CBSE Questions & Answers

Class 12 · Current Electricity

This is Physics Class 12 Current Electricity CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
According to Kirchhoff’s Loop Rule
  • A
    The absolute sum of changes in potential around any closed loop must be zero.
  • B
    The algebraic sum of changes in potential around any closed loop must be negative.
  • C
    The algebraic sum of changes in potential around any closed loop must be zero.
    Correct
  • D
    The algebraic sum of changes in potential around any closed loop must be positive.
2
For a Wheatstone bridge arrangement of four resistances – R1, R2, R3, R4 (Junction of R1 and R2 is connected to Anode and Junction of R3 and R4 to the cathode of the cell)The null-point condition is given by
  • A
    $\left( {{\text{R1}} + {\text{R3}}} \right) = \left( {{\text{R2}} + {\text{R4}}} \right)$
  • B
    $\left( {{\text{R1}} \times {\text{R3}}} \right) = \left( {{\text{R2}} \times {\text{R4}}} \right)$
  • C
    $\left( {{\text{R1}} - {\text{R3}}} \right) = \left( {{\text{R2}} - {\text{R4}}} \right)$
  • D
    $\left( {{\text{R1}}/{\text{R3}}} \right) = \left( {{\text{R2}}/{\text{R4}}} \right)$
    Correct
3
Potentiometer is
  • A
    basically a long piece of uniform wire
    Correct
  • B
    basically a short piece of non-uniform wire
  • C
    basically a loop of uniform wire
  • D
    basically a pair of uniform wires
4
The unit of current is
  • A
    newton
  • B
    coulomb
  • C
    joule
  • D
    Ampere
    Correct
5
resistivity has the units of
  • A
    Volt meter/Ampere
    Correct
  • B
    meter ×Ampere/Volt
  • C
    Volt ×Ampere
  • D
    Volt ×Ampere/meter
6
Unit of power is
  • A
    newton sec
  • B
    watt
    Correct
  • C
    joule
  • D
    newton
7
Ammeter is always used
  • A
    to simulate the element through which current is to be determined
  • B
    to simulate the element across which voltage is to be determined
  • C
    in parallel with the element through which current is to be determined
  • D
    in series with the element through which current is to be determined
    Correct
8
Kirchhoff’s second law is a consequence of
  • A
    Law of conservation of energy
    Correct
  • B
    Law of conservation of angular momentum
  • C
    Law of conservation of charge
  • D
    Law of conservation of momentum
9
An ammeter together with an unknown resistance in series is connected across two identical batteries each of emf 1.5 V. When the batteries are connected in series, the galvanometer records a current of 1A and when the batteries are in parallel, the current is 0.6A. Then the internal resistance of the battery is
  • A
    \({1 \over 3}\Omega \)
    Correct
  • B
    \({1 \over 5}\Omega \)
  • C
    \({1 \over 2}\Omega \)
  • D
    \({1 \over 4}\Omega \)
10
A battery is connected with a potentiometer wire. The internal resistance of the battery is negligible. If the length of the potentiometer wire of the same material and radius is doubled then
  • A
    Potential gradient becomes two times
  • B
    None of these
  • C
    Potential gradient does not change
    Correct
  • D
    Potential gradient becomes half
11
In a meter bridge experiment a balance point is obtained at a distance of 60 cm from the left end when unknown resistance R is in a left gap and 8 ohms resistor is connected in the right gap. When the position of R and 8 ohm resistor is interchanged the balance point will be at distance of
  • A
    30 cm
  • B
    60 cm
  • C
    40 cm
    Correct
  • D
    50 cm
12
A current is passed though two coils connected in series. The potential difference across the first coil of resistance 2 ohm is 5 volt. If the potential difference across the second coil is 12.5 volt the resistance of the second coil is
  • A
    5 ohm
    Correct
  • B
    12.5 ohm
  • C
    4 ohm
  • D
    7 ohm
13
If the length of the filament of a heater is reduced by \({{\rm{1}}0\% }\) the power of the heater will
  • A
    decrease by about \({{\rm{9}}\% }\)
  • B
    increase by about \({{\rm{19}}\% }\)
  • C
    increase by about \({{\rm{11}}\% }\)
    Correct
  • D
    Increase by about \({{\rm{9}}\% }\)
14
A Wheatstone bridge is balanced for four resistors R1, R2, R3 and R4 with a Lech lanche cell between A and C and a galvanometer between B and D. The positions of the cell and the galvanometer are interchanged. The balance will
  • A
    Change and can be obtained by changing R1
  • B
    Change and can be obtained by changing R4
  • C
    Not change
    Correct
  • D
    decrease by about \({{\rm{9}}\% }\)
15
An electric bulb rated for 500 watts at 100 volts is used in a circuit having 200 volt supply. The resistance R that must be put in series with the bulb so that the bulb draws 500 watts is
  • A
    10 ohms
  • B
    100 ohms
  • C
    20 ohms
    Correct