Science (English Medium) Class 12 - CBSE Important Questions

Obtain the expression for the cyclotron frequency.

A deuteron and a proton are accelerated by the cyclotron. Can both be accelerated with the same oscillator frequency? Give reason to justify your answer.

Write the expression for the force `vecF` acting on a particle of mass m and charge q moving with velocity `vecV` in a magnetic field `vecB` , Under what conditions will it move in (i) a circular path and (ii) a helical path?

Show that the kinetic energy of the particle moving in a magnetic field remains constant.

Obtain the expression for the magnetic energy stored in an inductor of self-inductance L to build up a current I through it.

A proton and an α-particle move perpendicular to a magnetic field. Find the ratio of radii of circular paths described by them when both have (i) equal velocities, and (ii) equal kinetic energy. 

Using Biot-Savart law, deduce the expression for the magnetic field at a point (x) on the axis of a circular current carrying loop of radius R. How is the direction of the magnetic field determined at this point?

The figure shows three infinitely long straight parallel current carrying conductors. Find the

1. magnitude and direction of the net magnetic field at point A lying on conductor 1,
2. magnetic force on conductor 2.

Depict the behaviour of magnetic field lines in the presence of a diamagnetic material?

Two identical coils P and Q each of radius R are lying in perpendicular planes such that they have a common centre. Find the magnitude and direction of the magnetic field at the common centre of the two coils, if they carry currents equal to I and \[\sqrt{3}\] I respectively.

A point charge q moving with speed v enters a uniform magnetic field B that is acting into the plane of the paper as shown. What is the path followed by the charge q and in which plane does it move?

 How does the path followed by the charge get affected if its velocity has a component parallel to \[\vec{B}\] .

 If an electric field \[\vec{E}\] is also applied such that the particle continues moving along the original straight line path, what should be the magnitude and direction of the electric field \[\vec{E}\] ?

With the help of a neat and labelled diagram, explain the principle and working of a moving coil galvanometer ?

Define current sensitivity of a galvanometer.

Velocity of light in glass is 2 × 10⁸ m/s and in air is 3 × 10⁸ m/s. If the ray of light passes from glass to air, calculate the value of critical angle.

Why does a galvanometer when connected in series with a capacitor show a momentary deflection, when it is being charged or discharged?

How does this observation lead to modifying the Ampere's circuital law?

Hence write the generalised expression of Ampere's law.

An electron moving horizontally with a velocity of 4 ✕ 10⁴ m/s enters a region of uniform magnetic field of 10⁻⁵ T acting vertically upward as shown in the figure. Draw its trajectory and find out the time it takes to come out of the region of magnetic 

field.

A straight wire of mass 200 g and length 1.5 m carries a current of 2 A. It is suspended in mid air by a uniform magnetic field B. What is the magnitude of the magnetic field?

Use Biot-Savart's law to find the expression for the magnetic field due to a circular loop of radius 'r' carrying current 'I', at its centre ?