Electro Magnetic Induction And Alternating Currents Question 515
Question: A nonconducting 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
Options:
A) the induced electric field is quadratic in time t
B) the force tangential to the ring is
C) until 2 seconds, the friction force does not come into play
D) the friction coefficient between the ring and the surface is
Show Answer
Answer:
Correct Answer: D
Solution:
-
Magnitude of induced electric field due to change in magnetic flux is given by
or
Here, E = induced electric field due to change in magnetic flux
Hence,
Ring starts rotating when torque of this force is greater than the torque due to maximum friction
Taking the limiting case,
or
It is given that ring starts rotating after 2 seconds So, putting t=2 seconds,
we get
