# Parameters of a Transformer

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An ideal step-down transformer is used to convert the AC voltage from the power line at 120V to 5.0V in an adapter for your laptop computer.

(a) The primary coil has 2000-turns, how many turns are in a secondary coil?

(b) If the average power consumption of your laptop is 80W, what is the average current in the primary coil and the current I in the secondary coil?

(c) What is the load resistance R in the secondary coil? Assume that it is an ideal transformer.

https://brainmass.com/physics/applied-physics/parameters-transformer-603663

## SOLUTION This solution is **FREE** courtesy of BrainMass!

Vp = 120 Volt

Vs = 5 Volt

a.

Np = 2000 turns

Ns = (VS/Vp)*Np = (5/120)*2000 = 83 (nearest integer value)

b.

Power, P = 80 W

Primary current

I1 = P/Vp = 80 / 120 = 2/3 Amp = 0.67 Amp

Secondary current,

I2 = P/Vs = 80/5 = 16 Amp

c.

P = I2^2 R

=> R = P/I2^2 = 80 / 16^2 = 0.3125 ohm.

https://brainmass.com/physics/applied-physics/parameters-transformer-603663