Question T5D05
From subelement T5 - T5D
What is the resistance of a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes?
Why is this correct?
Using Ohm's Law, resistance equals voltage divided by current: R = E / I. With 12 volts and 1.5 amperes, R = 12V ÷ 1.5A = 8 ohms. Choice A (18 ohms) incorrectly adds voltage and current. Choice B (0.125 ohms) inverts the calculation as I ÷ E. Choice D (13.5 ohms) incorrectly adds them together.
Memory tip
For Ohm's Law problems, identify what you're solving for first, then use the PIE circle method: cover the unknown value and the remaining shows your formula. Always check units match your expected answer range.
Learn more
Resistance opposes current flow — higher voltage pushes more current through the same resistance, while higher resistance restricts current for the same voltage. In practical circuits, knowing resistance helps determine appropriate component ratings and predict circuit behavior. This relationship becomes crucial when designing antenna matching networks, selecting appropriate fuses, and calculating power dissipation in resistive loads like dummy loads or heating elements in amateur radio equipment.
Think about it
Why do you think a 12-volt battery would produce different current amounts when connected to an 8-ohm resistor versus a 4-ohm resistor?