Magnetism

Question 1

Magnetic field

Answer 1

The region or space where a magnetic needle experiences a torque and rests in a definite direction

Question 2

Properties of lines of force

Answer 2

1. Lines of force start from north pole and end on south pole (inside magnet from S to N)
2. If we draw a tangent at a given point, it gives a direction of magnetic field at that point

Question 3

Oersted’s experiment

Answer 3

Oersted experimentally found that when electric current is passed through the conductor, magnetic field is produced in the surrounding space

Question 4

Biot-Savart Law

Answer 4

This law is used to determine the magnitude and direction of the field at a point due to current

Question 5

Ampere’s Circuital Law

Answer 5

The line integral of a magnetic field around any closed path is equal to the permeability of free space times the net current threading through the area enclosed by the path

Question 6

1 Tesla

Answer 6

If a charged particle of 1 C, moving with the velocity of 1 m/s, perpendicular to the magnetic field experiences a force of 1N then the magnetic field is said to be 1 T.

Question 7

Define 1 ampere

Answer 7

Current flowing through two parallel infinitely long conductors is said to be 1 ampere if separation between them is 1m and they experience a force of 2 x 10^-7 N/m in a free space

Question 8

Φ_B

Answer 8

Magnetic flux
Total number of magnetic field lines passing through a given area normally

Φ_B = ∫B∙dS (VECTORS PUT ARROW ON TOP OF B AND dS)

Unit: weber

Question 9

μ

Answer 9

Magnetic permeability
Ability of the material to allow magnetic lines of force to pass through it

μ = B/H

Wb/A-m²

Question 10

M (VECTOR)

Answer 10

Intensity of magnetisation

Magnetic moment per unit volume of a magnetised material

M = m/V (m and M are vectors)
m = magnetic dipole moment
V = Volume

Unit - A-m²/m³
= A/m

Question 11

H

Answer 11

Magnetising field or magnetic field intensity or applied magnetic field

Magnetic field used for magnetisation of the material

H = nI

Unit: A/m

Question 12

𝛘

Answer 12

Magnetic susceptibility
Intensity of magnetisation per unit magnetising field

𝛘 = M/H

No unit

Question 13

Relation bw susceptibility and relative permeability

Answer 13

μ_r = 1 + 𝛘_r

Question 14

Principle of MCG

Answer 14

When electric current flows in a coil placed in a magnetic field, a deflecting torque acts upon the coil

Question 15

Why is soft iron core used in MCG

Answer 15

Soft iron has high permeability and it is ferromagnetic in nature, so it is used to strengthen the magnetic field lines

Question 16

Why are cylindrical horseshoe magnets used in a moving coil galvanometer

Answer 16

They produce a radial field which is parallel to the coil i.e. angle bw B and area vector of coil is 90 degrees and the scale of the galvanometer is linear because of this

Question 17

How is a galvanometer converted into an ammeter

Answer 17

By connecting a low resistance shunt in parallel

Question 18

How is a galvanometer converted in a voltmeter

Answer 18

By connecting a high resistance shunt in series

Question 19

Current sensitivity

Answer 19

Deflection produced in the galvanometer when a unit current is passed through it

Question 20

Voltage sensitivity

Answer 20

Deflection produced in the galvanometer when a unit voltage is applied across the coil