Class 12 Physics Chapter 4 - Moving Charges and Magnetism MCQ and Assertion Questions

Two particles of masses \(m_{1}\) and \(m_{2}\) having charges \(q_{1}\) and \(q_{2}\) respectively are projected with the same velocity in a region of uniform magnetic field \(\vec{B}\) pointing vertically upward. If they describe circular paths as shown in the figure, one may conclude that :

A charged particle is moving in a uniform magnetic field \(\vec{B}\) with a constant speed v in a circular path of radius r. Which of the following graphs represents the variation of radius of the circle, with the magnitude of magnetic field \(\vec{B}\) ?

Four long straight thin wires are held vertically at the corners A, B, C and D of a square of side ‘a’, kept on a table and carry equal current ‘I’. The wire at A carries current in upward direction whereas the current in the remaining wires flows in downward direction. The net magnetic field at the centre of the square will have the magnitude :

Assertion (A) : The cylindrical soft iron core in a moving coil galvanometer only makes the magnetic field radial and does not affect the strength of the magnetic field.

Reason (R) : In a moving coil galvanometer, the plane of the coil is always perpendicular to the magnetic field.