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

Find the pd between A and B from the figure

A
2 V
B
4 V
Correct
C
8V
D
6V

The figure shows an unbalanced Wheatstone bridge. To balance the bridge:

A
15 ohm resistance should be reduced to 10 ohm
B
8 ohm resistance should be increased to 10 ohm
C
95 ohm resistance should be reduced to 90 ohm
Correct
D
48 ohm resistance should be increased to 50 ohm

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
6 ohm
B
5 ohm
Correct
C
7 ohm
D
12.5 ohm

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
60 cm
B
40 cm
Correct
C
80 cm
D
50 cm

The Wheatstone bridge is balanced for four resistors R1,R2,R3 and R4 with a cell of emf 1.46 V. The cell is now replaced by another cell of emf 1.08 V. To obtain the balance again

A
All the four resistance should be changed
B
No resistance needs to be changed
Correct
C
Both the resistance R1 and R4 should be changed
D
Resistance R4 should be changed only

If the length of the filament of a heater is reduced by ${{\rm{1}}0\% }$ the power of the heater will

A
increase by about 11%
Correct
B
increase by about 19%
C
decrease by about 29%
D
Increase by about 9%

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 R1 and R4
C
Change and can be obtained by changing R4
D
Not change
Correct

A Wheatstone bridge ABCD is balanced with a galvanometer between the points B and D. At balance the resistance between the points B and D is :

A
Between zero and infinite
B
Infinite
Correct
C
Zero
D
None of the above

The ratio of the currents I1 when switch S is off and I2 when switch S is on is

A
1:1
B
2:1
C
1:2
Correct
D
Zero:2

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
50 ohms
B
100 ohms
C
10 ohms
D
20 ohms
Correct

In the circuit shown below, the galvanometer G will show zero deflection

A
only if S is closed
B
none of these
Correct
C
only if S is open
D
in all cases

A milliammeter of range 10 mA has a coil of resistance 1 Ω.To use it as an ammeter of range 1 A, the required shunt must have a resistance of

A
$\frac{1}{{101\Omega }}$
B
$\frac{1}{{99\Omega }}$
Correct
C
$\frac{1}{{9\Omega }}$
D
$\frac{1}{{100\Omega }}$

A capacitor is charged and then made to discharge through a resistance. The time constant is $\tau $In what time will the potential difference across the capacitor decrease by 10%

A
$\tau {\text{ln}}\left( {{\text{1}}0/{\text{9}}} \right)$
Correct
B
$\tau {\text{ln}}\left( {{\text{11}}/{\text{9}}} \right)$
C
$\tau {\text{ln}}\left( {0.{\text{9}}} \right)$
D
$\tau {\text{ln}}\left( {0.{\text{1}}} \right)$

Meter Bridge is based on the principle of

A
Kirchhoff's node Rule
B
potentiometer
C
Wheatstone bridge
Correct
D
Kirchhoff's loop Rule

Meter Bridge is used to

A
determine unknown power P
B
determine unknown emf e
C
determine unknown voltage v
D
determine unknown resistance R
Correct