ISC (Science) ISC Class 12 - CISCE Important Questions for Physics (Theory)

A moving coil galvanometer has a coil of resistance 59 Ω. It shows a full-scale deflection for a current of 50 mA. How will you convert it to an ammeter having a range of 0 to 3A?

When does a moving charged particle nor experience any force while moving through a uniform magnetic field?

Using Ampere's circuital law, obtain an expression for the magnetic flux density 'B' at a point 'X' at a perpendicular distance 'r' from a long current-carrying conductor.
(Statement of the law is not required).

Write the expression for the Lorentz force F in vector form.

PQ is a long straight conductor carrying a current of 3A as shown in Figure below. An electron moves with a velocity of 2 x 10⁷ ms^-1 parallel to it. Find the force acting on the electron.

State Biot Savart law. 

Two infinitely long current carrying conductors X and Y are kept parallel to each other, 24 cm apart in a vacuum. They carry currents of 5A and 7A respectively, in the same direction, as shown in the figure below. Find the position of a neutral point, i.e., a point where resultant magnetic flux density is zero. (Ignore earth’s magnetic field). 

Define Ampere in terms of force between two current carrying conductors.

A long straight wire AB carries a current of 5A. P is a proton travelling with a velocity of 2 × 10⁶ m/s, parallel to the wire, 0.2 m from it and in a direction opposite to the current, as shown in Figure below. Calculate the force which magnetic field of the current carrying conductor AB exerts on the proton.

A moving coil galvanometer of resistance 55 Ω produces a full scale deflection for a current of 250 mA. How will you convert it into an ammeter with a range of 0 - 3A?

Using Ampere’s circuital law, obtain an expression for magnetic flux density ‘B’ at a point near an infinitely long and straight conductor, carrying a current I.

Lorentz force in vector form is ______.

Assertion: When an electric current is passed through a moving coil galvanometer, its coil gets deflected.

Reason: A circular coil produces a uniform magnetic field around itself when an electric current is passed through it.

Using Biot-Savart law, show that magnetic flux density 'B' at the centre of a current carrying circular coil of radius R is given by: `B = ("μ"_0I)/(2R)` where the terms have their usual meaning.

When current flowing through a solenoid decreases from 5A to 0 in 20 milliseconds, an emf of 500V is induced in it.

1. What is this phenomenon called?
2. Calculate coefficient of self-inductance of the solenoid.

The figure below shows a circuit containing an ammeter A, a galvanometer G and a plug key K. When the key is closed:

A circular coil having N turns of radius R carrying a current I is used to produce a magnetic field B at its centre O.

If this coil is opened and rewound such that the radius of the newly formed coil is 2R, carrying the same current I, what will be the magnetic field at the centre O?

The figure below are two long, parallel wires carrying current in the same direction such that I₁ < I₂.

1. In which direction will wire I₁ move?
2. If the direction of the current I₂ is reversed, in which direction will the wire I₁ move now?

A galvanometer of resistance 100 Ω gives a full-scale deflection for a potential difference of 200 mV.

1. What must be the resistance connected to convert the galvanometer into an ammeter of the range 0-200 mA?
2. Determine resistance of the ammeter.

An electron moving along positive X axis with a velocity of 8 ×10⁷ms^-1 enters a region having uniform magnetic field B = 1.3 × 10^-3 T along positive Y axis.

1. Explain why the electron describes a circular path.
2. Calculate the radius of the circular path described by the electron.