A uniform magnetic field B exists in a cylindrical region of radius 10 cm as shown in figure. A uniform wire of length 80 cm and resistance 4.0Ω is bent into a square frame and is placed with one side along a diameter of the cylindrical region. If the magnetic field increases at a constant rate of 0.010 T/s, find the current induced in the frame.

Given:
Radius of cylindrical region ![]()
Length of wire =80cm
Resistance of the wire ![]()
Rate of increase of magnetic field =0.01T/s![]()
Area of loop inside magnetic field =area of semicircle of radius 0.1m
![]()
We know that,
Flux (ϕ) of magnetic field (B) through the loop of cross section area A in the magnetic field is given by
![]()
![]()
Since magnetic field is perpendicular to the loop the flux becomes
![]()
Rate of change of magnetic field wrt. time is given by
![]()
(since area of cross section in magnetic field does not change with time, A remains constant)
Now,
by faraday’s law of electromagnetic induction
…(i)
Where
ϵ =emf produced
ϕ =flux of magnetic field
using eqn.(i) the emf induced in the loop is given by
![]()
Hence the current through the loop (i) of resistance R is
![]()
Putting the values of A, R and
in the above eqn. the magnitude of current is
![]()
Therefore current induced in the frame is ![]()
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