The figure shows?moving rod MN that makes sliding electrical contact with statio

Question

The figure shows?moving rod MN that makes sliding electrical contact with stationary wires connected to a resistor. The rod of length 3.7 cm is moving perpendicular to ? uniform magnetic field of magnitude 7.6 10-3 T (a) Which end (M or N) of the rod is at lower electric potential? (b) In which direction does the current flow through the resistor? from right to left from left to right (c) If the speed of the rod decreases, what happens to the current? The current decreases. The current increases. (d) If the current through the 31 ? resistor is 2.9 × 10-6 A, what is the induced voltage in the wire? (e) What is the speed of the wire? m/s (f) if the magnitude of the magnetic field were doubled, what would be the effect(s) on the system? Assume that the speed of the rod is unchanged. (Select all that apply. O The induced current would be halved. O The induced current would double. O The induced voltage would double O The induced voltage would be halved

Explanation / Answer

(a) M is lower potential point

(b) From right to left

(c) The current decreases

(d) R = 31 ohm,    I = 2.9*10^-6 A, d = 3.7 cm,   B = 7.6*10^-3 T

The emf is generated by sliding the conducting rod in a direction perpendicular to the magnetic field

The emf driving the current is equal to vBd where d is the length of the section of wire connecting the rails. (The work done per unit charge (voltage) is vBd, when a charge moves from one end of the moving wire to the other end.)

Voltage = vBd = IR = 2.9*10^-6*31 = 89.9*10^-6 V

(e) Speed = v = IR/(Bd) = 89.9*10^-6/(7.6*10^-3*0.037) = 0.32 m/s

(f) The induced current would double

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