Physics Test - ...

An electron, a proton and an alpha particle having the same kinetic energy are moving in circular orbits of radii r_e, r_p, r_α respectively in a uniform magnetic field B. The relation between r_e, r_p, r_α is:

The magnetic field inside a solid conducting long wire at distance r from its axis is given as B = B₀r³ where B0 is constant. Which of the following relations correctly represents current enclosed in the loop of radius r shown in figure:

Two short bar magnets with magnetic moments 400 ab-amp cm² and 800 ab-amp cm² are placed with their axis in the same straight line with similar poles facing each other and with their centers at 20 cm from each other. Then the force of repulsion is

A magnetic needle lying parallel to a magnetic field required W units of work to turn it through 60°. The torque required to maintain the needle in this position will be

A coil PQRS carrying a current i A is placed in a powerful horse shoe magnet NS of uniform magnetic field as shown in the figure. If A is the area of the coil and θ is the inclination of the plane of the coil with the magnetic field in equilibrium, then, the deflecting couple will be,

A charge moving with velocity v in X - direction is subjected to a field of magnetic induction in negative X - direction. As a result, the charge will

An electron moving around the nucleus with an angular momentum l has a magnetic moment

An iron rod of volume 10⁻³ m³ and relative permeability 1000 is placed as core in a solenoid with 10 turns cm⁻¹. If a current of 0.5 A is passed through the solenoid, then the magnetic moment of the rod will be :

Three long wires, with identical currents, either directly into or directly out of the page, are placed at three corners of a square in four different arrangements as shown. The correct order of the magnitude of the net magnetic field at the centre of the square is

A uniform magnetic needle is suspended from its centre by a thread. Its upper end is now loaded with a mass 50 mg , and the needle becomes horizontal. If the strength of each pole is 98.1 A cm and g = 981 cm s⁻², then the vertical component of earth's magnetic induction is