SAT Subject Physics Practice Question 552: Answer and Explanation
8. A step down transformer changes the high input voltage used in our houses (120V) into the low voltage used to charge an electric razor (24V). What must be the ratio of the turns of wire from the primary side of the transformer to the secondary side?
Correct Answer: A
The correct answer is (A). The ratio between the number of turns in the primary and the number of turns in the secondary is equal to the ratio of the primary voltage and the secondary voltage 120V/24V = 5:1.