What does a transformer ratio of 20:1 signify?

A transformer ratio of 20:1 signifies that there are 20 turns on the primary winding for every 1 turn on the secondary winding. This means that the transformer is designed to step down voltage. In this scenario, for every single turn in the secondary, there are 20 turns in the primary, leading to a higher voltage on the primary side compared to the secondary side.

The transformer operates under the principle that the ratio of the voltages in the primary and secondary is equal to the ratio of the number of turns in the respective windings. Therefore, with a greater number of turns on the primary, the voltage on the primary side is increased compared to a smaller number of turns on the secondary side.

This also has implications for current. Since power (the product of voltage and current) must be conserved (neglecting losses), a lower voltage on the secondary side corresponds to a higher current, as per the power equation (P = VI). Hence, if the voltage is stepped down from the primary, the current is stepped up proportionally.

Overall, option B correctly captures the relationship implicit in the transformer's turns ratio.