Question T5D09
From subelement T5 - T5D
What is the current through a 24-ohm resistor connected across 240 volts?
Why is this correct?
The correct answer is C (10 amperes). Using Ohm's Law, current equals voltage divided by resistance: I = E / R = 240 volts / 24 ohms = 10 amperes. The distractors show common calculation errors: A (24,000) multiplies instead of dividing, B (0.1) inverts the calculation incorrectly, and D (216) subtracts resistance from voltage instead of dividing.
Memory tip
For Ohm's Law problems, always identify what you're solving for first, then use the PIE circle method: cover what you want to find, and the remaining variables show the operation. Current problems always involve division when you have voltage and resistance.
Learn more
In practical amateur radio circuits, this calculation helps determine if your components can handle the current flow. A 24-ohm resistor carrying 10 amperes would dissipate 2,400 watts of power (P = I²R), which would require a very large power resistor or proper heat sinking. Most small resistors are rated for much lower power levels, typically 1/4 to 2 watts for common applications.
Think about it
Why do you think option A shows 24,000 amperes, and what would actually happen if that much current tried to flow through a 24-ohm resistor?