I.e. in Fig. 20.34, a metal bar moves at constant velocity in a constant magneti
ID: 1543410 • Letter: I
Question
I.e. in Fig. 20.34, a metal bar moves at constant velocity in a constant magnetic field. That field is directed into the page. (a) the direction of the induced current through the bar is (1) up, (2) down, (3) there is no current. Why? (b) If the magnitude of the magnetic field is 0.55 T, what is the current in the bar? Neglect the resistances of the bar and wires, (c) What are the magnitude and direction of the force on the bar? (d) What is the power required by the force on the bar? (e) Compare your answer to part (d) to the rate of joule heating in the resistor. They should be the same. Are they? Explain why they should be.Explanation / Answer
From the figure, Given that,
B = 0.55 T
R = 10 ohm
V = 2 m/s
L = 0.50 m
(a)
As given that magnetic field in inside the page and velocity is towards left.
From the right hand thum law, direction of Force is downward.
so, direction of current is downward.
(b)
we know that,
l = E / R = B*v*L / R
l = 0.55*2*0.5 / 10
l = 0.055 A
(c)
F = B*I*L
F = 0.55*0.055*0.5 = 0.015 N
direction = towards the right (opposite the velocity)
(d)
Power P = F*v
P = 0.015*2 = 0.030 W
(e)
rate of heating = P' = l^2*R
P' = (0.055)^2*10 = 0.030 W
P = P'
answer