A 75 W high intensity lamp has a resistance of 12 ohms when burning. The
lamp’s power comes from the secondary of a small transformer, the primary of
which is connected to a 120 V circuit.
What is the ratio of the number of turns on the secondary winding?
What is the minimum current through the primary when the lamp is on?
lamp’s power comes from the secondary of a small transformer, the primary of
which is connected to a 120 V circuit.
What is the ratio of the number of turns on the secondary winding?
What is the minimum current through the primary when the lamp is on?
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From P = V²/R ..
V = √(P*R) = √900 = 30V
Vs = 30V
Ns/Np = Vs/Vp = 1/4 ... ...► Ns = 1/4Np
120v * I = 75W
I = 75/120 .... .... ► I = 0.625 A
V = √(P*R) = √900 = 30V
Vs = 30V
Ns/Np = Vs/Vp = 1/4 ... ...► Ns = 1/4Np
120v * I = 75W
I = 75/120 .... .... ► I = 0.625 A