A rectangular coil of sides ' l ' and ' b ' carrying a current I is subjected to a uniform magnetic field B → acting perpendicular to its plane. Obtain the expression for the torque acting on it.

Magnetic moment associated with the current-carrying coil is m → = I A n ^ = I l b n ^ where n ^ is a unit vector perpendicular to the plane of the coil. Torque τ → = m → × B → = I l b n ^ × B → = I l b 0 → = 0 → This is because n ^ and B → are either parallel to antiparallel vectors.

A moving coil galvanometer of resistance G gives a full scale deflection for a current I g Use the suitable circuit diagram to convert it into an ammeter of range 0 to I I > I g . Deduce the expression for the shunt required for this conversion. Hence write the expression for the resistance of the ammeter thus obtained.

Given: The resistance of galvanometer, = G Current in galvanometer for full-scale deflection, I g The range of ammeter, 0 to I Let the required shunt resistance is S and the current through the shunt is I - I g The shunt resistance is connected in parallel with the galvanometer. Hence, P.D. across the galvanometer = P.D. across the shunt I g G = I - I g S ⇒ S = I g I - I g × G Now the total resistance of ammeter, R A = G S G + S < S

EASY

12th CBSE

IMPORTANT

Earn 100

Two long straight parallel conductors carry steady currents $I_{1}$ and $I_{2}$ separated by a distance $d$ . If the currents are flowing in the same direction, show how the magnetic field set-up in one produces an attractive force on the other. Obtain the expression for this force. Hence define one ampere.

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>Text Based Exercises>Q 24

Derive a formula for the force between two parallel straight conductors carrying current in opposite directions and write the nature of the force. Hence, define an ampere.

MEDIUM

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Text Based Exercises>Q 25

Derive an expression for the torque on a rectangular coil of area

A

, carrying a current

I

and placed in a magnetic field

B

. The angle between the direction of

B

and vector perpendicular to the plane of the coil is

θ

. Indicate the direction of the torque acting on the loop.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Text Based Exercises>Q 26

A rectangular coil of sides

' l'

and

' b'

carrying a current

I

is subjected to a uniform magnetic field

\vec{B}

acting perpendicular to its plane. Obtain the expression for the torque acting on it.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Text Based Exercises>Q 27

A rectangular loop of area

A

, having

N

turns and carrying a current of

I

ampere is held in a uniform magnetic field

B

. Write the expression for the maximum torque experienced by the loop.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Text Based Exercises>Q 27

A rectangular loop of area

A

, having

N

turns and carrying a current of

I

ampere is held in a uniform magnetic field

B

. In which orientation, will the loop be in stable equilibrium?

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Text Based Exercises>Q 28

State the principle of a moving coil galvanometer. Show that the current passing through the coil is directly proportional to the deflection of the coil.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Text Based Exercises>Q 29

A moving coil galvanometer consists of a rectangular coil of

N

turns, each of area

A

, suspended in a radial magnetic field of flux density

B

. Derive the expression for the torque on the coil, when current

I

passes through it. Draw a suitable labelled diagram.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Text Based Exercises>Q 30

A moving coil galvanometer of resistance

G

gives a full scale deflection for a current

I_{g}

Use the suitable circuit diagram to convert it into an ammeter of range

0

I (I > I_{g})

. Deduce the expression for the shunt required for this conversion. Hence write the expression for the resistance of the ammeter thus obtained.

Two long straight parallel conductors carry steady currents I1 and I2 separated by a distance d. If the currents are flowing in the same direction, show how the magnetic field set-up in one produces an attractive force on the other. Obtain the expression for this force. Hence define one ampere.

Important Questions on Magnetic Effect of Current

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