According to Ampere's law, magnetic fields are related to the electric current produced in them. The law specifies the magnetic field that is associated with a given current or vice-versa, provided that the electric field doesn’t change with time. Ampere’s Law can be stated as: The magnetic field created by an electric current is proportional to the size of that electric current with a constant of proportionality equal to the permeability of free space.

Describe the construction of suspended coil galvanometer, draw labelled diagram of it. Prove that current flowing in the coil of galvanometer is directly proportional to the deflection generated in the coil.

Construction: It consists of a rectangular coil wound on a non-conducting metallic frame and is suspended by phosphor bronze strip between the pole-pieces (N and S) of a strong permanent magnet. A soft iron core in cylindrical form is placed between the coil. One end of coil is attached to suspension wire which also serves as one terminal (T1) of galvanometer. The other end of coil is connected to a loosely coiled strip, which serves as the other terminal (T2). The other end of the suspension is attached to a torsion head which can be rotated to set the coil in zero position. A mirror (M) is fixed on the phosphor bronze strip by means of which the deflection of the coil is measured by the lamp and scale arrangement. The levelling screws are also provided at the base of the instrument The pole pieces of the permanent magnet are cylindrical so that the magnetic field is radial at any position of the coil. Principle and working: When current (I) is passed in the coil, torque τ acts on the coil, given by τ = N I A B sin θ where θ is the angle between the normal to plane of coil and the magnetic field of strength B, N is the number of turns in a coil. When the magnetic field is radial, as in the case of cylindrical pole pieces and soft iron core, then in every position of coil the plane of the coil, is parallel to the magnetic field lines, so that θ = 90 ° a n d sin 90 ° = 1 Deflecting torque, τ = N I A B If C is the torsional rigidity of the wire and θ is the twist of suspension strip, then restoring torque =Cθ For equilibrium, deflecting torque = restoring torque i . e . N I A B = C θ θ = N A B C I . . . . . . . . . . . . ( i ) i . e . θ ∝ I deflection of coil is directly proportional to current flowing in the coil and hence we can construct a linear scale.

Write the name of any two rules to find the direction of magnetic field.

The direction of the magnetic field produced by a current carrying straight conductor. can be obtained by using (i) Right hand thumb, rule, and (ii) Maxwell's corkscrew rule. i] Right-hand thumb rule : If the current-carrying straight wire is held in the right hand with the thumb pointing towards the direction of current, then the direction of fingers encircling the conductor give the direction of the magnetic field . ii] Maxwell's corkscrew rule: If a right handed screw is rotated along the current carrying straight wire in the direction of current , then the direction in which the screw rotates gives the direction of the magnetic field .

According to Ampere's law, magnetic fields are related to the electric current produced in them. The law specifies the magnetic field that is associated with a given current or vice-versa, provided that the electric field doesn’t change with time. Ampere’s Law can be stated as: The magnetic field created by an electric current is proportional to the size of that electric current with a constant of proportionality equal to the permeability of free space.

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 4 - Moving Charges and Magnetism>Rajasthan Board-2020>Q 11

EASY

12th Rajasthan Board

IMPORTANT

Earn 100

What is Helmholtz coils? Prove that the value of a uniform magnetic field obtained in the Helmholtz coil is $1.432$ times the magnetic field generated by each coil at its centre. Draw necessary graph also.

Important Questions on Moving Charges and Magnetism

EASY

12th Rajasthan Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 4 - Moving Charges and Magnetism>Rajasthan Board-2018>Q 1

Write the definition of figure of merit of Galvanometer.

MEDIUM

12th Rajasthan Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 4 - Moving Charges and Magnetism>Rajasthan Board-2018>Q 2

Obtain an expression for magnetic field due to infinitely long straight current carrying conductor by using Amperes law.

EASY

12th Rajasthan Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 4 - Moving Charges and Magnetism>Rajasthan Board-2018>Q 3

The resistance of a galvanometer is

99 Ω

. The necessary current for full scale deflection is

1 mA

. If a shunt of

1 Ω

is connected with galvanometer then find the value of maximum current which can be measured by this galvanometer.

EASY

12th Rajasthan Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 4 - Moving Charges and Magnetism>Rajasthan Board-2019>Q 4

Write formula for force on a current carrying conductor in magnetic field.

EASY

12th Rajasthan Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 4 - Moving Charges and Magnetism>Rajasthan Board-2019>Q 5

Write Ampere's law.

MEDIUM

12th Rajasthan Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 4 - Moving Charges and Magnetism>Rajasthan Board-2019>Q 6

Draw a diagram and derive an expression for magnetic field due to an infinitely long straight current carrying conductor at any point.

MEDIUM

12th Rajasthan Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 4 - Moving Charges and Magnetism>Rajasthan Board-2019>Q 7

Write Biot-Savart law.

MEDIUM

12th Rajasthan Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 4 - Moving Charges and Magnetism>Rajasthan Board-2019>Q 8

Write the working of cyclotron in brief. Draw a schematic sketch of the cyclotron showing path of accelerated charged particles (ions) in both dees. Derive expression for cyclotron frequency.