JEE Advanced Practice Quiz

Question 1

A circular conducting loop of radius r and resistance R is placed in a uniform magnetic field B perpendicular to its plane. The field decreases uniformly to zero in time t. The total charge that flows through the loop during this interval is

Accepted Answer

πr^2B/R

Question 2

A metal rod of length l moves with constant velocity v on two parallel conducting rails in a uniform magnetic field B perpendicular to the plane of the rails. The motional emf across the rod is

Accepted Answer

Blv

Question 3

A square loop of side a and resistance R lies in the plane of the page. A long straight wire carrying current I is parallel to one side of the loop and at distance d from the nearer side. If current in the wire increases at rate dI/dt, the induced emf in the loop is

Accepted Answer

(μ0a/2π)(dI/dt) ln((d+a)/d)

Question 4

A conducting rod of length l slides without friction on horizontal rails separated by distance l, completing a circuit of total resistance R. A uniform magnetic field B acts vertically downward. If the rod is pulled with constant speed v, the external force required is

Accepted Answer

B^2l^2v/R

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