Question

A transformer is to be used to provide power for a computer disk drive that needs 6.4 V (rms) instead of the 120 V (rms) from the wall outlet. The number of turns in the primary is 300, and it delivers 500 mA (the secondary current) at an output voltage of 6.4 V (rms). (a) Should the transformer have more turns in the secondary compared to the primary, or fewer turns

Answer 1

Answer:

The secondary coil should have fewer turns compared to the primary coil.

Explanation:

$N_p$ = Number of turns in primary coil = 300

$N_s$ = Number of turns in secondary

$V_p$ = Voltage in primary coil = 120 V

$V_s$ = Voltage in secondary coil = 6.4 V

We have the relation

$\dfrac{N_p}{N_s}=\dfrac{V_p}{V_s}\\\Rightarrow N_s=\dfrac{N_p}{V_p}\times V_s\\\Rightarrow N_s=\dfrac{300}{120}\times 6.4\\\Rightarrow N_s=16$

The secondary coil has 16 turns which is less than the turns in the primary coil.