What does the number of turns on the primary coil of a transformer affect?

The number of turns on the primary coil of a transformer plays a crucial role in determining the voltage output. According to the principles of electromagnetic induction, the voltage across the primary and secondary coils of a transformer is proportional to the number of turns in each coil.

In a step-up transformer, for instance, if there are more turns on the secondary coil than on the primary coil, the voltage output will be greater than the voltage input. Conversely, in a step-down transformer, where the secondary coil has fewer turns than the primary, the voltage output will be less than the input. This relationship can be described mathematically by the formula:

[ \frac{V_p}{V_s} = \frac{N_p}{N_s} ]

where ( V_p ) and ( V_s ) are the voltages across the primary and secondary coils, and ( N_p ) and ( N_s ) are the number of turns on the primary and secondary coils, respectively. This principle illustrates how changing the number of turns on the primary coil directly influences the voltage output from the transformer, making this option the correct choice.