Question T5D07
From subelement T5 - T5D
What is the current in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms?
Why is this correct?
The correct answer is D. 1.5 amperes. Using Ohm's Law formula I = E / R, we calculate: I = 120 volts / 80 ohms = 1.5 amperes. Option A (9600 amperes) incorrectly multiplies voltage and resistance. Option B (200 amperes) divides resistance by voltage instead of voltage by resistance. Option C (0.667 amperes) appears to use an incorrect calculation altogether.
Memory tip
Remember the Ohm's Law circle diagram: cover what you're solving for, and the remaining values show the operation. When finding current (I), cover I and you see E over R, meaning divide voltage by resistance.
Learn more
In practical amateur radio circuits, calculating current helps determine proper fuse ratings and component power handling. A typical HF transceiver drawing 20 amperes at 13.8 volts represents about 276 watts of power consumption. Understanding current calculations becomes essential when sizing power supplies, selecting appropriate wire gauges per NEC standards, and ensuring circuits operate within safe thermal limits for continuous duty cycles.
Think about it
Why do you think increasing resistance in a circuit always decreases current when voltage stays constant?