Question

48. A transformer is used to supply a 12-V model train with power from a 110-V wall plug. The train operates at 50Wofpower.(a)What is the rms current in the secondary coil of the transformer? (b) What is the rms current in the primary coil?(c)What is the ratio of the number of primary to secondary turns? (d) What is the resistance of the train? (e) What is the resistance seen by the 110-V source?

Answer 1

Data given.

Voltge in primary coil , V1 = 110 V

Voltage in secondary coil, V2 =12 V

Power , P = 50 W

Part (a). Rms Current in secondary coil.

I secondary = power / V2

Is = 50/12 = 4.167 A

Part-b

Rms current in primary coil.

I primary = power / V1

Ip = 50/110 =   0.4545 A

Part-c

The primary is the 110 V side of the transformer, and the secondary is the 12 V side.

The turn ratio is directly proportional to the voltage ratio.

So,   N primary / N secondary = 110/ 12

= 9.167

D -

Resistance in of train.

R2 = V2 / Is

= 12/4.167

= 2.87 ohm

Part E

Resistance at source.

R1 = V1/Ip

= 110/0.4545

= 242 ohm

answered by: anonymous