Question

A particular transformer has 20,000 loops in its primary coil, and 200 loops in its secondary coil. This transformer supplies power to houses in Europe, where residential voltage is 220V. What was the voltage of the transmission line that lead into the transformer?

Answer 1

Explanation: A transformer takes high voltage electricity with a small current and changes it into low voltage electricity with a large current, or vice versa. A step-up transformer turns low-voltage electricity into high-voltage electricity while dropping the current. A step-down transformer changes high-voltage electricity into low-voltage electricity.

If we change the number of turns in the coils we change the induced emf. This allows us to change (transform) the voltage from the primary to the secondary coil.

The Turns Rule is:

Ns/Np= Vs/Vp

Where,

Ns = number of turns on the secondary coil

Np = number of turns on the primary coil

Vs = voltage across the secondary coil

Vp = voltage across the primary coil

So if number of turns on the secondary coil(200 turns) is lesser than on the primary coil(20000 turns), the output voltage will be lesser than the input voltage. This is called a step down transformer.

Hence, The output voltage as per the given question can be obtained as follows:

Let x be the output voltage and the input voltage is given as 220V.

Ns/Np=Vs/Vp

That is,

200/20000= x/220

x= 200×220/20000 = 2.2V

Therefore the output voltage is 2.2V