The question is about step up/down transformers A television tube requires a hig

Question

The question is about step up/down transformers
A television tube requires a high voltage to work properly,and uses 80 W of power when its running. The power supplied to itfrom the secondary winding of a transformer; the primary winding isconnected to the voltage source of 120 V (rms) (whats available atthe receptacle on the wall). When the tube is on, the tubedraws 6.7 mA of current from the secondary windings.
a) what must be the ratio of the number of turns in thesecondary to that in the primary windings, Ns/Np, of thistransformer?
b) what must be the voltage in the secondary?
A television tube requires a high voltage to work properly,and uses 80 W of power when its running. The power supplied to itfrom the secondary winding of a transformer; the primary winding isconnected to the voltage source of 120 V (rms) (whats available atthe receptacle on the wall). When the tube is on, the tubedraws 6.7 mA of current from the secondary windings.
a) what must be the ratio of the number of turns in thesecondary to that in the primary windings, Ns/Np, of thistransformer?
b) what must be the voltage in the secondary?

Explanation / Answer

power P = 80 W voltage V p = 120 V current i p = P / V = 0.66666 A current in secondary i s = 6.7 mA = 6.7 * 10 ^ -3A (a). we know N s / Np = i p / i s                                    = 99.5 (b). we know Vp / V s = Np / Ns                              Vs = V p ( Ns / Np )                                   = 11940 V

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