A transformer is to be used to provide power for a computer disk drive that needs 7.0 V (rms) instead of the 120 V (rms) from the wall outlet. The number of turns in the primary is 390, and it delivers 500 mA (the secondary current) at an output voltage of 7.0 V (rms). The current in the primary was 29.1
Find the number of turns in the secondary.