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

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

Step-by-step 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

`(N_p)/(N_s)=(V_p)/(V_s)\\\Rightarrow N_s=(N_p)/(V_p)* V_s\\\Rightarrow N_s=(300)/(120)* 6.4\\\Rightarrow N_s=16`

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