Compare the current sensitivity and voltage sensitivity of the following moving coil galvanometers: M 1 and M 2 : N 1 = 30 , A 1 = 1 .5 × 10 - 3 m 2 , B 1 = 0 .25 T , R 1 = 20 Ω , N 2 = 35 , A 2 = 2 .0 × 10 - 3 m 2 , B 2 = 0 .25 T , R 2 = 30 Ω . You are given that the springs in the two meters have the same torsional constants.

The current sensitivity of the moving coil galvanometer For the 1 st galvanometer, I S 1 = N 1 B 1 A 1 k = 30 × 0 .25 × 1 .5 × 10 − 3 k = 1 .125 × 10 − 2 k For the 2 nd galvanometer, I s 2 = N 2 B 2 A 2 k = 35 × 0 .25 × 2 × 10 - 3 k = 1 .75 × 10 - 2 k The ratio of current sensitivity, I s 1 : I s 2 = 9 : 14 Voltage sensitivity is given as, V S = α V = α I R = I S R Hence, For the 1 st galvanometer, V S 1 = I S 1 R 1 = 1 .125 × 10 − 2 k × 20 For the 2 nd galvanometer, V S 2 = I S 2 R 2 = 1 .75 × 10 − 2 k × 30 The ratio of voltage sensitivity, V s 1 : V s 2 = 27 : 28

EASY

12th CBSE

IMPORTANT

Earn 100

The coil of a galvanometer consists of $250$ turns of fine wire wound on a $2.0 cm \times 1.0 cm$ rectangular frame. It is suspended in a uniform radial magnetic field of strength $2, 000 G$ . A current of $10^{- 4} A$ produces an angular deflection of $30 °$ in the coil. Find the torsional constant of its suspension.

Important Questions on Magnetic Effect of Current

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems For Practice>Q 3

A moving coil galvanometer is placed in a radial magnetic field of

0.2 T

. The galvanometer coil has

200

turns and area of

1 .6 \times 10^{- 4} m^{2}

. The torsion constant of the suspension fibre is

10^{- 6} N m \deg^{- 1}

. Determine the maximum current that can be measured by this galvanometer if its scale can accommodate a deflection of

45 °

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems For Practice>Q 4

The coil of moving coil galvanometer is

40 mm

long and

25 mm

wide. It has

100

turns and is suspended in a radial magnetic field of

10^{- 2} T

. It the suspension fibre has a torsional constant of

10^{- 8} N m \deg^{- 1}

. find the current sensitivity of the moving coil galvanometer.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems For Practice>Q 5

A coil of a moving coil galvanometer twists through

45 °

when a current of

1

micro‐ampere is passed through it. If the area of the coil is

10^{- 5} m^{2}

and it has

1000

turns, find the magnetic field of the magnet of the galvanometer. The restoring torque per unit twist of the galvanometer coil is

10^{- 4} N m \deg^{- 1}

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems For Practice>Q 6

The coil of a pivoted‐type galvanometer has

50

tums and encloses an area of

6 m^{2}

. The magnetic field in the region in which the coil swings is

0.01 T

and is radial. The torsional constant of the hair spring is

1 .0 \times 10^{- 8} {Nmdeg}^{- 1}

. Find the angular deflection of the coil for a current of

1 m A

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems For Practice>Q 7

A rectangular coil of area

8 \times 10^{- 4} m^{2}

is suspended freely in a radial magnetic field of induction

2 \times 10^{- 2} Wb m^{- 2}

. When a current of

5 μ A

is passed through the coil, it deflects through

60 °

. The torsional constant of the suspension is

3 .821 \times 10^{- 9} N m {rad}^{- 1}

Find the number of turns of the coil.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems For Practice>Q 8

A galvanometer needs

25 mV

for a full scale deflection of

50

divisions. Find its voltage sensitivity. What must be its resistance if its current sensitivity is

1 div / 20 μA

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems For Practice>Q 9

If the current sensitivity of a moving coil galvanometer is increased by

20 %

, its resistance also increases by

1.5

times. How will the voltage sensitivity of the galvanometer be affected?

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems For Practice>Q 10

Compare the current sensitivity and voltage sensitivity of the following moving coil galvanometers: $M_{1}$ and $M_{2}$ :

$N_{1} = 30, A_{1} = 1 .5 \times 10^{- 3} m^{2}$ ,

$B_{1} = 0 .25 T, R_{1} = 20 Ω$ ,

$N_{2} = 35, A_{2} = 2 .0 \times 10^{- 3} m^{2}$ ,

$B_{2} = 0 .25 T, R_{2} = 30 Ω$ .

You are given that the springs in the two meters have the same torsional constants.

The coil of a galvanometer consists of 250 turns of fine wire wound on a 2.0 cm×1.0 cm rectangular frame. It is suspended in a uniform radial magnetic field of strength 2,000 G. A current of 10-4 A produces an angular deflection of 30° in the coil. Find the torsional constant of its suspension.

Important Questions on Magnetic Effect of Current

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