What is the maximum safe amperage draw of the secondary winding for a 60 VA transformer with a 12 V output?

What is the maximum safe amperage draw of the secondary winding for a 60 VA transformer with a 12 V output?

• A. 7.2 Amps
• B. 5 Amps
• C. 720 Amps
• D. 0.2 Amps

Answer: (B)

The key relationship here is the transformer’s apparent power: S = V × I. The secondary winding can deliver up to its rated VA when the voltage is the rated secondary voltage. So the maximum safe current is Imax = S ÷ Vout. With a 60 VA transformer and a 12 V output, Imax = 60 ÷ 12 = 5 A. This makes sense because 12 V × 5 A equals 60 VA, matching the transformer’s rating. The other numbers don’t fit the rating: 7.2 A would imply about 86 VA, exceeding the limit; 720 A would require unrealistically high power; 0.2 A would only give about 2.4 VA, well below the rating.

The key relationship here is the transformer’s apparent power: S = V × I. The secondary winding can deliver up to its rated VA when the voltage is the rated secondary voltage. So the maximum safe current is Imax = S ÷ Vout.

With a 60 VA transformer and a 12 V output, Imax = 60 ÷ 12 = 5 A. This makes sense because 12 V × 5 A equals 60 VA, matching the transformer’s rating.

The other numbers don’t fit the rating: 7.2 A would imply about 86 VA, exceeding the limit; 720 A would require unrealistically high power; 0.2 A would only give about 2.4 VA, well below the rating.