2- In the figure, a bar is in contact with a pair of parallel rails, which are i

Question

2- In the figure, a bar is in contact with a pair of parallel rails, which are in contact with a resistance of 20 S2. The distance between the parallel rails is 0.18 m. If a steady and uniform magnetic field of 0.86 T, is perpendicular to the plane of the rails and directed out of the page. The bar is in motion with velocity v- 0.1 m/s a) What is the induced current through the resistor R and in which b) How much force is exerted on the bar by the magnetic field, and in c) How much, and in which direction, is an external force needed to direction? which direction? keep the bar moving in the same direction with the same speed olv ???

Explanation / Answer

a) as the bar is moving area of the loop decreases so magnetic flux also decreases

magnetic flux = B*A

according to lenz's law

the loop will try to maintain flux which is in upward direction.

so flux is upward when the current is in counter clock wise direction

that is from a to b

b) f = ma

f = Bil

i = emf/R

emf = work /w = w/q = f*//q = qvBl/q = vBl

so i = vB^2l^2/R

i = 0.1*0.86^2*0.18^2/20

i = 1.19*10^-4 A

f = Bil = 0.86*1.19*10^-4*0.18 = 1.84*10^-5 N

c) according to newtons third law

same amount of force acting externally inorder to keep the same speed.and opposite to the direction

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