How do I apply Ohm's Law in electrical calculations?

Ohm's Law is fundamental in electricity: U = R × I (voltage = resistance × current). On the job site, you use it constantly to size conductors and protection devices.

Practical example: For a 15 A circuit at 120 V, total resistance is R = 120 ÷ 15 = 8 Ω. Power P = U × I = 120 × 15 = 1,800 W.

Important variants: I = U ÷ R (to find current), R = U ÷ I (for resistance), and P = U × I (power). On the CMEQ exam, questions often use mixed circuits where you must combine Ohm's Law with series/parallel circuit rules.

Remember: in series, current is constant; in parallel, voltage is constant across each branch.