Question T5D08
From subelement T5 - T5D
What is the current through a 100-ohm resistor connected across 200 volts?
Why is this correct?
The correct answer is C (2 amperes). Using Ohm's Law, I = E / R, where current equals voltage divided by resistance. Substituting the values: I = 200 volts / 100 ohms = 2 amperes. The wrong answers result from calculation errors: A (20,000) multiplies instead of dividing, B (0.5) inverts the calculation, and D (100) ignores the voltage entirely.
Memory tip
For Ohm's Law problems, always identify what you're solving for first, then select the correct formula. Remember the relationship: voltage and resistance are inversely related to current — higher resistance means lower current for the same voltage, while higher voltage means higher current for the same resistance.
Learn more
In practical amateur radio circuits, this calculation helps determine if components can handle the current flow. A 100-ohm resistor carrying 2 amperes would dissipate P = I²R = 4 watts of power as heat. Understanding these relationships is crucial for circuit design, component selection, and preventing equipment damage from overcurrent conditions in transmitters and power supplies.
Think about it
Why do you think option A shows 20,000 amperes — what mathematical mistake would lead someone to that unrealistic answer for a simple resistor circuit?