Question

A step-down transformer is used for recharging the batteries of portable electronic devices. The turns ratio N2/N1 for a particular transformer used in a DVD player is 1:13. When used with 120-V (rms) household service, the transformer draws an rms current of 20.0 mA from the house outlet. Find
(a) the rms output voltage of the transformer and
(b) the power delivered to the DVD player.

Answer 1

Answer:

(a) Rms output voltage of the transformer will be 9.23 volt

(b) Power delivered to the DVD player will be 2.4 watt

Explanation:

We have given turn ratio of the transformer $\frac{N_2}{N_1}=\frac{1}{13}$

Primary voltage $V_1=120volt$

(a) For transformer we know that $\frac{N_2}{N_1}=\frac{V_2}{V_1}$

$\frac{1}{13}=\frac{V_2}{120}$

So $V_2=9.23volt$

(b) Primary current is given as $I_1=20mA$

For transformer we know that

$\frac{N_2}{N_1}=\frac{I_1}{I_2}$

$\frac{1}{13}=\frac{20}{I_2}$

$I_2=260mA=0.26A$

So power delivered will be $P=VI=9.23\times 0.260=2.4watt$