1. A coil has 280 turns and is positioned such that its plane is perpendicular t

Question

1. A coil has 280 turns and is positioned such that its plane is perpendicular to a constant magnetic field, B = 0.877 T. The coil magically shrinks in area from Ainitial = 0.540 m2 to Afinal = 0.112 m2 in a time Delta T = 0.00151 seconds. What would be the induced voltage across the leads of the coil?

2. A transformer has Nprimary = 2300 turns and Nsecondary = 680 turns. The primary potential is Vprimary = 120 Vrms. Determine the secondary potential, Vsecondary. A load, R = 440 is attached to the secondary coil. Determine the current in the secondary coil and the current in the primary coil.

Explanation / Answer

induced emf is defiend as the rate of change of magnetic flux

in mathematical form,

induced emf e = NAdB/dt

where A = area

N = no. of tunrs

dB/dt = rate of change of amgnetic flux

so here emf e = 280* (0.540-0.112) * 0.877/(0.00151)

emf e = 69.6 KVolts

b)

For a transformer, you can start with

N2/N1 = V2/V1

680/2300 = V2/120

V2 = 35.5 V

Part B)

Apply V = IR

35.5 = I(440)

I = .0807 Amps (80.7 mA) in the secondary

For the Primary....

IV = IV

I(120) = (.0807)(35.5)

I = .0239 A (23.9 mA)

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