What is the transformer secondary wattage for 12V at 20A?

What is the transformer secondary wattage for 12V at 20A?

• A. 240 W
• B. 12 W
• C. 20 W
• D. 2400 W

Answer: (A)

The key idea is that the power available from the transformer’s secondary is the product of its voltage and its current (P = V × I). With a 12-volt secondary delivering 20 amperes, the wattage is 12 × 20 = 240 watts. In practical terms this is the VA rating, and for a resistive load that’s close to the actual watts, accounting for efficiency and power factor. The other options don’t match the simple V × I calculation: 12 W would be 12 V at 1 A, 20 W would be 12 V at about 1.67 A, and 2400 W would be 12 V at 200 A. So 240 W is the correct result.

The key idea is that the power available from the transformer’s secondary is the product of its voltage and its current (P = V × I). With a 12-volt secondary delivering 20 amperes, the wattage is 12 × 20 = 240 watts. In practical terms this is the VA rating, and for a resistive load that’s close to the actual watts, accounting for efficiency and power factor.

The other options don’t match the simple V × I calculation: 12 W would be 12 V at 1 A, 20 W would be 12 V at about 1.67 A, and 2400 W would be 12 V at 200 A. So 240 W is the correct result.