Q1: A step-up transformer has 80 turns on its primary coil and 1200 turns on its secondary coil. The

primary circuit is supplied with an alternating current at 120 V.

a) What voltage is being applied across the secondary circuit?

b) The current in the secondary circuit is 2.0 A. What current is in the primary circuit?

c) What are the power input and output of the transformer?

a. 1.8 kV b. 30 A c. power input = 3.6 kW, power output = 3.6 kW

Explanation:

a. Since turns ratio N₁/N₂ = V₁/V₂ where N₁ = number of turns of primary coil = 80 turns, N₂ = number of turns of secondary coil = 1200 turns, V₁ = voltage in primary circuit = 120 V and V₂ = voltage in secondary circuit = unknown

So, V₂ = N₂V₁/N₁

= 1200 * 120 V/80

= 1800 V

= 1.8 kV

b. Also, N₁/N₂ = I₂/I₁ where I₁ = current in primary circuit = unknown and I₂ = current in secondary circuit = 2.0 A

So, I₁ = N₂I₂/N₁

= 1200 * 2.0 A/80

= 30 A

c. The power input of the transformer P₁ = I₁V₁

= 30 A * 120 V

= 3600 W

= 3.6 kW

The power output of the transformer P₂ = I₂V₂

= 2 A * 1800 V

= 3600 W

= 3.6 kW