MOTORS AND GENERATORS QN

[bloop]

Hi, I need help with the below question, thank you

An 85% efficient transformer is shown below (image is too big)

Primary coil = 90 turns.
Secondary coil = 300 turns.

If a current of 2mA flows in the secondary coil and power output is 100W, the primary voltage is what?

Answer is 17638 V

[pikachu975]

Hi, I need help with the below question, thank you

An 85% efficient transformer is shown below (image is too big)

Primary coil = 90 turns.
Secondary coil = 300 turns.

If a current of 2mA flows in the secondary coil and power output is 100W, the primary voltage is what?

Answer is 17638 V

P = VI
100 = 2x10^-3 x V
Vs = 50,000

Vp/Vs = np/ns
Vp = 50000*90/300
Vp = 15,000 but it's 85% efficiency
So Vp = 15,000/0.85
Vp = 17,647 V