Science (English Medium) कक्षा १२ - CBSE Important Questions for Physics

Which of the following substances are diamagnetic?

Bi, Al, Na, Cu, Ca and Ni

What are permanent magnets? Give one example ?

Which of the following substances are para-magnetic?

Bi, Al, Cu, Ca, Pb, Ni

The susceptibility of a magnetic material is − 2.6 × 10⁻⁵. Identify the type of magnetic material and state its two properties.

The horizontal component of the earth’s magnetic field at a place is B and angle of dip is 60°. What is the value of vertical component of earth’s magnetic field at equator?

The relative magnetic permeability of a magnetic material is 800. Identify the nature of magnetic material and state its two properties.

A magnetic needle, free to rotate in a vertical plane, orients itself vertically at a certain place on the Earth. What are the values of (i) Horizontal component of Earth’s magnetic field and (ii) angle of dip at this place?

What is the angle of dip at a place where the horizontal and vertical components of the Earth’s magnetic field are equal?

Where on the surface of Earth is the angle of dip zero?

A horizontal straight wire of length L extending from east to west is falling with speed v at right angles to the horizontal component of Earth’s magnetic field B. 

(i) Write the expression for the instantaneous value of the e.m.f. induced in the wire. 

(ii) What is the direction of the e.m.f.?

(iii) Which end of the wire is at the higher potential?

Write two characteristics of a material used for making permanent magnets ?

Why is the core of an electromagnet made of ferromagnetic materials?

Draw magnetic field line when a (i) diamagnetic, (ii) paramagnetic substance is placed in an external magnetic field. Which magnetic property distinguishes this behaviour of the field line due to the substances?

Why should the material used for making permanent magnets have high coercivity?

An a-particle and a proton of the same kinetic energy are in turn allowed to pass through a magnetic field `vec"B"`, acting normal to the direction of motion of the particles. Calculate the ratio of radii of the circular paths described by them.

Answer the following question.
Define the term "Intensity" in the photon picture of electromagnetic radiation.

Identify the following magnetic materials :

Deduce the expression for the torque `vec"τ"` acting on a planar loop of area `vec"A"` acting on a planar loop of area `vec"B"`. If the loop is free to rotate, what would be its orientation in stable equilibrium?

If the magnetizing field on a ferromagnetic material is increased, its permeability ______.

A uniform magnetic field gets modified as shown in figure when two specimens A and B are placed in it.

(a)	(b)

1. Identify the specimen A and B.
2. How is the magnetic susceptibility of specimen A different from that of specimen B?