Question

. If you are designing a transformer for a cell phone charging cable and need to step down the voltage from the primary coil to the secondary by half, which coil should have more turns O The primary coil should have more turns O The secondary coil should have more turns O The two coils should have the same number of turns 8. From one coil of a transformer to another, which of the following quantities ALWAYS stays constant (does not change)? O Voltage O Current O Energy O Resistance

Answer 1

In a step down transformer, the turns in primary are more than the turns in secondary, as

V_{​​​​​​O}/V_{​​​​​​i} = N_{​​​​​​s}/N_{​​​​​​p}

Where, V_​o is the output voltage V_{​​​​​​i} is the input voltage, Ns & Np are no. Of turns in secondary and primary.

And the information given is that output voltage is less than input voltage.

While transferring the voltage changes, and hence current may change depending upon the resistance in the coils, but power is equal in both the coils, giving that energy is constant.