Ohm's Law, Without the Algebra Panic

Ohm's law describes a relationship between three quantities: voltage (E, measured in volts), current (I, measured in amps), and resistance (R, measured in ohms). The relationship is E = I × R. That's the whole law. Everything else you'll see on the exam is just this equation rearranged to solve for whichever variable you don't already know.

The trick that trips people up isn't the math, it's that the exam gives you the formula in three different forms and expects you to pick the right one under time pressure. If you know voltage and resistance and need current, you rearrange to I = E ÷ R. If you know voltage and current and need resistance, it's R = E ÷ I. You don't need to memorize three formulas separately. Memorize E = I × R, and rearrange it on the spot using basic algebra: whatever you're solving for, isolate it on one side.

A concrete way to hold this in your head: think of voltage as electrical pressure pushing electrons through a circuit, resistance as whatever is restricting that flow, and current as the actual rate of flow that results. More pressure with the same restriction means more flow. More restriction with the same pressure means less flow. That's the entire intuition, and it maps directly onto the formula: E goes up, I goes up (if R is constant). R goes up, I goes down (if E is constant).

Where this shows up beyond the direct calculation questions: power. Power (P, in watts) is P = E × I, voltage times current. Combine that with Ohm's law and you can derive power from any two of the three original quantities. If a question gives you voltage and resistance and asks for power, first find current with I = E ÷ R, then find power with P = E × I. Two steps, not one, but each step is a formula you already know.

A practical study tactic: don't just memorize the rearranged formulas, work backward from the answer choices. If a question asks for current in amps and one answer choice is a number in the hundreds while the others are in single digits, and you're dealing with a small battery-powered circuit, the hundreds-value answer is almost certainly wrong before you do any math at all. The exam pool reuses the same handful of numeric setups repeatedly (12 volts and various resistances is common, since it maps to typical amateur equipment), so once you've worked through a few of these by hand, the arithmetic stops being the hard part.