Final answer:
For a motor with constant resistance, if the voltage is increased from 240V to 480V, the current will be halved to maintain constant power, resulting in a current of 10A.
Step-by-step explanation:
If a motor has a current draw of 20A at 240V, what will the amperage be if 480V is applied?
To answer this question, we need to consider the relationship between voltage, current, and resistance in a motor. Electric motors have a characteristic known as resistance, and according to Ohm's Law V = IR (Voltage equals Current times Resistance), if the resistance remains constant and the voltage is increased, the current will also increase proportionally. However, in the scenario of an ideal transformer, power is conserved which implies that P = VI (Power equals Voltage times Current) will remain the same. Therefore, if the voltage is doubled, the current must be halved to maintain the same power. Hence, when the voltage is increased from 240V to 480V, the current would reduce to half of its original value to maintain constant power.
In this case, the motor drawing 20A at 240V would draw 10A at 480V, assuming the motor can handle the increased voltage without other limiting factors such as saturation or thermal limits. So the correct answer is A) 10 A.