A. Consider the following experimental setup. A single loop of conducting wire i

Question

A. Consider the following experimental setup. A single loop of conducting wire is connected to a resistor as shown in the diagram. A magnet is then taken and passed through the wire at a constant speed, north side first.

1. Suppose that the magnetic flux changes from 4.90 Wb to 2.70 Wb in a time of 0.32 s. What is the energy dissipated through the resistor during this time (resistance = 0.4 omega)?

2. Suppose that the speed with which the magnet moves is constant and equal to 0.60 m/s. What is the minimal magnetic force (assumed to be constant) that the magnet would feel during the 0.32 s interval?

B. In a television set the power needed to operate the picture tube comes from the secondary coil of a transformer. The primary coil of the transformer is connected to a 120-V receptacle on a wall. The picture tube of the television set uses 104 W and has a resistance of 18.9 kilo-omega. Find the turns ratio Ns/Np of the transformer.

Explanation / Answer

1. induced emf , e = d(flux) / dt

e = (4.90 - 2.70) / 0.32

e = 6.875 Volt

P = e^2 / R = 6.875^2 / 0.4 = 118.16 W

Energy = P t = 118.16 x 0.32 = 37.8 J

2. P = F. v

118.16 = F (0.60)

F = 197 N

(B ) P = V^2 / R

104 = V^2 / (18.9 x 10^3)

V = 1402 Volt

that is Vs = V = 1402 Volt

Ns / Np = Vs / Vp = 1402 /120 = 11.7 Or 12

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