NATE Air Conditioning and Heat Pumps Practice Exam

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According to Ohm's Law, what will happen if voltage to a heater element is increased by 10%?

The Btuh output will increase by 5%
The current draw will decrease by 10%
The current draw will increase by 10%
The heater will overheat

The correct answer is: The current draw will increase by 10%

Ohm's Law states that the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit is given by the equation V = I × R. If the voltage supplied to a heater element is increased by 10%, the current draw will also increase in relation to the change in voltage, provided that the resistance remains constant. In a resistive heating element, the power output (in Btuh, or British thermal units per hour) is directly related to the square of the current (P = I²R), which means that an increase in current due to a voltage increase will result in a more than proportional increase in power output. Therefore, an increase in voltage by a certain percentage leads to an increase in current by approximately the same percentage, because the resistance does not change. As a result, with a 10% increase in voltage, the current will correspondingly increase, aligning with the response that indicates the current draw will increase by 10%. This understanding of electrical principles is critical for effectively working with heater elements in air conditioning and heating systems.