Question

In a primary coil 5 A current is flowing on 220 volts. In a primary coil 5 A current is flowing on 220 volts. the ratio of number of turns in secondary coil and primary coil will be :

• A. 1 : 10
• B. 10 : 1
• C. 1 : 1
• D. 11 : 1

Answer 1

The correct option is B 10 : 1

Answer is B.
A transformer takes high-voltage electricity with a small current and changes it into low-voltage electricity with a large current, or vice versa. That is, step up or step down the voltage in a circuit. 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 is more than on the primary coil, the output voltage will be higher than the input voltage. This is called a step up transformer.
Let input voltage be 220 V and the output voltage be 2200 V.
Ns/Np=Vs/Vp;
That is, Vs/Vp = 2200/220 = 10/1 = 10:1.
The ratio of the voltages is equal to ratio of the number of turn in the windings.
Therefore, the ratio of number of turns in secondary coil and primary coil will be 10:1.