# What voltage is supplied to the primary winding of a transformer with 4000 turns, if the secondary winding

**What voltage is supplied to the primary winding of a transformer with 4000 turns, if the secondary winding has 100 turns and the load is supplied with a voltage of 20V at a current of 4A. Resistance of the secondary winding 0.5 Ohm.**

Given:

W1 = 4000 turns – the number of turns in the primary winding of the transformer;

W2 = 100 turns – the number of turns in the secondary winding of the transformer;

U = 20 Volts – voltage supplied to the load;

I = 4 Amperes – current strength;

r = 0.5 Ohm – resistance of the secondary winding of the transformer.

It is required to determine U (Volt) – what voltage is supplied to the primary winding of the transformer.

Find the load resistance:

R = U / I = 20/4 = 5 ohms.

Then the EMF of the secondary winding is equal to:

e = I * (R + r) = 4 * (5 + 0.5) = 4 * 5.5 = 22 Volts.

The transformation ratio is:

n = W1 / W2 = 4000/100 = 40.

Then the voltage on the primary winding will be equal to:

U = e * n = 22 * 40 = 880 Volts.

Answer: the voltage on the primary winding is 880 volts.