Question

The potential difference of electricity distributed to neighborhoods is around 1.5x10⁴V, but the difference in homes is 1.2x10²V. A transformer is used to “step down the voltage.” If the secondary coil of the transformer has 160 turns, then how many turns should the primary coil have?

In an ideal transformer, the power is conserved. Determine the current in the line before it reaches the transformer if the current in the house should be 250A.

Answer 1

We know that in transformers,

Np/Ns = Vp/Vs = Is/Ip

Given that

Np = Number of turns in primary coil = ?

Ns = Number of turns in secondary coil = 160 turns

Vp = Potential difference in primary coil = 1.50*10^4 V

Vs = Potential difference in secondary coil = 1.20*10^2 V

So,

Np = Ns*(Vp/Vs)

Np = 160*(1.5*10^4/120) = 20000 turns = 2.0*10^4 turns

Since, Np/Ns = Vp/Vs = Is/Ip

Is = current to secondary coil = 250 A

So,

Ip = Is*(Vs/Vp)

Ip = 250*(120/(1.50*10^4))

Ip = 2 Amp = current in the line

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