For a transformer with a 2:1 turns ratio and a 480 V primary, what is the secondary voltage (ideal transformer)?

For a transformer with a 2:1 turns ratio and a 480 V primary, what is the secondary voltage (ideal transformer)?

• A. 960 V
• B. 480 V
• C. 240 V
• D. 120 V

Answer: (C)

The key idea is that in an ideal transformer the output voltage scales with the turns ratio. A 2:1 turns ratio means the primary has twice as many turns as the secondary, so the secondary voltage is half the primary voltage. With a 480 V primary, the secondary voltage is 480 × (Ns/Np) = 480 × (1/2) = 240 V. This matches the given answer because the voltage drops by the same factor as the turns ratio. If the turns ratio were different, the secondary voltage would change accordingly: a ratio that doubles the turns on the secondary would produce 960 V, a 1:1 ratio would keep it at 480 V, and a 1:4 ratio would yield 120 V.

The key idea is that in an ideal transformer the output voltage scales with the turns ratio. A 2:1 turns ratio means the primary has twice as many turns as the secondary, so the secondary voltage is half the primary voltage. With a 480 V primary, the secondary voltage is 480 × (Ns/Np) = 480 × (1/2) = 240 V.

This matches the given answer because the voltage drops by the same factor as the turns ratio. If the turns ratio were different, the secondary voltage would change accordingly: a ratio that doubles the turns on the secondary would produce 960 V, a 1:1 ratio would keep it at 480 V, and a 1:4 ratio would yield 120 V.