Magnetics-03-SUBJECTIVE SOLVED
SUBJECTIVE SOLVED EXAMPLES
1. A circular loop of radius R is bent along a diameter and given a
shape as shown in figure. One of the semi-circles (KNM) lies in y
the x-z plane and the other one (KLM) in the y-z plane with their
centres at origin. Current I is flowing through each of the semi- x
circles as shown in figure. z
→
A particle of charge q is released at the origin with a velocity V iˆ . Find the instantaneous force
→ on the particle. Assuem that space is gravity free.
Solution :Magnetic field at the centre of a circular wire of radius R carrying a current I is given by
B 0I
2R
In this problem, currents are flowing in two semi-circles, KLM in the y-z plane and KNM in the x- z plane. The centres of these semi-circles coincide with the origin of the Cartesian system of axes.
→ 1 0I ˆ
BKLM
(i)
2 2R
→ 1 0I ˆ
BKNM
(j)
2 2R
The total magnetic field at the origin is
B 0I (ˆi ˆj)
0 4R
It is given that a particle of charge q is released at the origin with a velocity V = - instantaneous force acting on this particle is given by
V0ˆi . The
→ →
f q[V B]
q(V ˆi) 0I (ˆi ˆj)
0 4R
q V00I ˆ ˆ ˆ
4R
[(i) (i j)
q V00I (kˆ) .
4R
2. A coil of radius R carries current I. Another concentric coil of radius (r <
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