A galvanometer of resistance G is converted into a voltmeter to measure upto V volts by connecting a resistance R 1 in series with the coil. If a resistance R 2 is connected in series with it, then it can measure upto V 2 volts. Find the resistance, in terms of R 1 and R 2 , required to be connected to convert it into a voltmeter that can read upto 2 V . Also find the resistance G of the galvanometer in terms of R 1 and R 2 .

For voltmeter of range V , V = I g G + R 1 ...(i) For voltmeter of range V / 2 , V 2 = I g G + R 2 .....(ii) On dividing (i) by (ii) 2 = G + R 1 G + R 2 or 2 G + R 2 = G + R 1 ∴ G = R 1 − 2 R 2 Let R 3 be the resistance required for conversion into voltmeter of range 2 V . then, 2 V = I g G + R 3 ...(iii) 2 = G + R 3 G + R 1 or 2 G + 2 R 1 = G + R 3 ∴ R 3 = G + 2 R 1 = R 1 − 2 R 2 + 2 R 1 = 3 R 1 - 2 R 2 .

MEDIUM

12th CBSE

IMPORTANT

Earn 100

If a galvanometer is connected in series with a high resistance so that potential drop across the galvanometer is $1 / n$ th of the total applied voltage, then show
that the combined resistance of the galvanometer and the series resistor is n times the resistance of the galvanometer i.e., $R_{V} = n R_{g}$ .

Important Questions on Magnetic Effect of Current

MEDIUM

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>HOTS Problems on Higher Order Thinking Skills>Q 34

A galvanometer of resistance

G

is converted into a voltmeter to measure upto

V

volts by connecting a resistance

R_{1}

in series with the coil. If a resistance

R_{2}

is connected in series with it, then it can measure upto

\frac{V}{2}

volts. Find the resistance, in terms of

R_{1}

and

R_{2}

, required to be connected to convert it into a voltmeter that can read upto

2 V

. Also find the resistance

G

of the galvanometer in terms of

R_{1}

and

R_{2}

MEDIUM

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>GUIDELINES TO NCERT EXERCISES>Q 4.1.

A circular coil of wire consisting of

100

turns, each of radius

8.0 cm

carries a current of

0.40 A

. What is the magnitude of the magnetic field

B

at the center of the coil? Take,

μ_{0} = 4 π \times 10^{- 7} H / m

MEDIUM

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>GUIDELINES TO NCERT EXERCISES>Q 4.2.

A long straight wire carries a current of

35 A

. What is the magnitude of the field

B

at a point

20 cm

from the wire? Take,

μ_{0} = 4 π \times 10^{- 7} H / m

MEDIUM

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>GUIDELINES TO NCERT EXERCISES>Q 4.3.

A long straight wire in the horizontal plane carries a current of

50 A

in the north to south direction. Give the magnitude and direction of

B

at a point

2.5 m

east of the wire. Take,

μ_{0} = 4 π \times 10^{- 7} H / m

MEDIUM

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>GUIDELINES TO NCERT EXERCISES>Q 4.4.

A horizontal overhead power line carries a current of

90 A

in the east to west direction. What is the magnitude and direction of the magnetic field due to the current

1.5 m

below the line? Take,

μ_{0} = 4 π \times 10^{- 7} H / m

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>GUIDELINES TO NCERT EXERCISES>Q 4.5.

What is the magnitude of magnetic force per unit length on a wire carrying a current of

8 A

and making an angle of

30 °

with the direction of a uniform magnetic field of

0.15 T

MEDIUM

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>GUIDELINES TO NCERT EXERCISES>Q 4.6.

3.0 cm

wire carrying a current of

10 A

is placed inside a solenoid perpendicular to its axis. The magnetic field inside the solenoid is given to be

0 \cdot 27 T

. What is the magnetic force on the wire?

MEDIUM

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>GUIDELINES TO NCERT EXERCISES>Q 4.7.

Two long and parallel straight wires A and B carrying currents of

8.0 A

and

5.0 A

in the same direction are separated by a distance of

4.0 cm

. Estimate the force on a

10 cm

section of wire A.

If a galvanometer is connected in series with a high resistance so that potential drop across the galvanometer is 1/nth of the total applied voltage, then show that the combined resistance of the galvanometer and the series resistor is n times the resistance of the galvanometer i.e., RV=nRg.

Important Questions on Magnetic Effect of Current

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