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Physics Guru is an online education and competitive examinations preparation portal founded by Manish Verma, an IIT Madras alumnus, providing learning resources for competitive examinations.

The emphasis is on conceptual understanding, analytical thinking and problem solving rather than simply memorising formulas and standard methods.

The objective is to help students understand what they are learning and develop the ability to solve problems they have not seen before.

Q & A (Induced Electric Field)

A non conducting ring of mass m and radius R has a charge Q uniformly distributed over its circumference. The ring is placed on a rough horizontal surface such that the plane of the ring is parallel to the surface. A vertical magnetic field $B = {B_0}{t^2}$ Tesla is switched on. After t second from switching on the magnetic field the ring is just about to rotate about vertical axis through its centre. Find the friction coefficient between the ring and the surface.

Solution (.wmv download)