Question

The function of those little black transformers that clog your power strips is to step down line voltage to run small electronic gadgets. Suppose a fax machine uses an ideal transformer with a primary voltage of 120 V and primary windings. If the secondary voltage is 12 V find
A.) The number of turns on the secondary
B.) If the fax machine at idle draws enough current to dissipate 6 W, find the current that must flow in the primary.



Find the resonant frequency of a circuit that has a 400 mH inductor and a 30 nF capacitor connected in series.

Answer 1

A. Np/Ns = Vp/Vs = 120/12 = 10/1.
Turns Ratio = 10:1

Ts = Tp/10

To find the number of turns on the secondary(Ts), we need to know the
number of turns on the primary(Tp).

B. 120 * I = 6 W. Solve for I.

Fr = 1/(2pi*Sqrt(LC)
Fr = 1(6.28*Sqrt( 0.40*30*10^-9) =
8.33 Million Hertz = 8.33 mHz.