UP-BOARD-XII SERIES

Physics

Magnetism

14 previous year questions.

Volume: 14 Ques

Yield: Medium

High-Yield Trend

9

2025

5

2023

Chapter Questions
14 MCQs

01

PYQ 2023

medium

physics ID: up-board

The field produced around current carrying conductor is:

1

Only electric

2

Only magnetic

3

Both electric and magnetic

4

None of these

02

PYQ 2023

medium

physics ID: up-board

If actual angle of dip is and is the angle of dip in a plane at an angle from the magnetic meridian, then is

1

2

3

4

03

PYQ 2023

medium

physics ID: up-board

Obtain the formula for the magnetic field at the centre of a current carrying circular coil with the help of Biot-Savart law.

04

PYQ 2023

medium

physics ID: up-board

A coil of area is placed in a uniform magnetic field of . If the coil has 100 turns and of current is passed in it, then find: Magnetic dipole moment of the coil Maximum torque on the coil

05

PYQ 2023

medium

physics ID: up-board

Establish the formula for the force acting between two parallel current carrying straight wires of infinite length. Explain when and why the force between both current carrying conductors becomes (i) attractive and (ii) repulsive.

06

PYQ 2025

easy

physics ID: up-board

Establish the formula of magnetic dipole moment.

Official Solution

Correct Option: (1)

Step 1: Understanding the Concept: The magnetic dipole moment is a quantity that describes the magnetic strength of a magnet or a current-carrying loop. We can establish its formula by analyzing the torque experienced by a current loop in a uniform magnetic field and drawing an analogy with the torque on an electric dipole. Step 2: Torque on a Current Loop in a Magnetic Field: Consider a rectangular loop PQRS with length and breadth , carrying a current I. Let this loop be placed in a uniform magnetic field such that the normal to the plane of the loop makes an angle with . \begin{center} \end{center} The magnetic forces on the arms QR and SP are equal, opposite, and collinear, so they cancel each other out and produce no torque. The force on arm PQ, using the formula , is (directed into the page). The force on arm RS is (directed out of the page). These two forces, and , are equal and opposite, forming a couple that exerts a torque on the loop. The torque ( ) is given by the product of one of the forces and the perpendicular distance between their lines of action. The perpendicular distance between the forces is . Since the area of the loop is , we can write: If the loop has N turns, the torque is multiplied by N: Step 3: Establishing the Formula for Magnetic Dipole Moment: This expression for torque on a current loop is analogous to the torque experienced by an electric dipole (with dipole moment ) in a uniform electric field ( ): By comparing the two torque equations, we can define a magnetic analogue to the electric dipole moment. This quantity is called the magnetic dipole moment, denoted by m (or ). Comparing with , we can establish the formula for the magnitude of the magnetic dipole moment as: The magnetic dipole moment is a vector quantity, . Its direction is perpendicular to the plane of the current loop, given by the right-hand thumb rule (if the fingers curl in the direction of the current, the thumb points in the direction of ). Using this vector definition, the torque equation can be written in a more general vector form: Step 4: Final Answer: The formula for the magnetic dipole moment of a planar current loop with N turns, area A, and carrying current I is established as .

07

PYQ 2025

medium

physics ID: up-board

An electron projected towards East is deflected towards North by a magnetic field. The direction of magnetic field may be

1

towards West

2

towards South

3

perpendicular to the plane upwards

4

perpendicular to the plane downwards

08

PYQ 2025

medium

physics ID: up-board

What is meant by the concept of matter-wave of de Broglie ? Establish the relation for de Broglie wavelength in terms of kinetic energy.

09

PYQ 2025

medium

physics ID: up-board

The work function of photoelectric surface is 4.0 eV. Radiation of frequency Hz is incident on it. Calculate the maximum velocity of emitted photo-electron.

10

PYQ 2025

medium

physics ID: up-board

What is the solenoid ? Obtain the expression for magnetic field inside a long current carrying solenoid.

11

PYQ 2025

medium

physics ID: up-board

Differentiate between paramagnetic, diamagnetic and ferromagnetic substances by giving one example of each.

12

PYQ 2025

medium

physics ID: up-board

How does the magnetic susceptibility () of paramagnetics change with respect to absolute temperature (T) ?

1

T

2

T

3

= constant

4

e

13

PYQ 2025

medium

physics ID: up-board

The unit of magnetic dipole moment is

1

A m

2

A m

3

A/m

4

m /A

14

PYQ 2025

medium

physics ID: up-board

The magnetic susceptibility of paramagnetic substance varies with absolute temperature as:

1

2

3

4