Plain-English Meaning
V = IR: a bigger voltage (V) pushes more current (I) through, but resistance (R) fights the flow. If you double the voltage, you double the current (for fixed resistance). Everyday example: a 12 V car battery driving 1 Ω of resistance draws 12 A of current.
Keep charge, field, potential, and current distinct. That single habit fixes a large fraction of electromagnetism errors.
Deeper Explanation
Ohm's law is empirical — it holds for ohmic materials (resistors) but not for diodes, transistors, or non-linear elements. Resistance R = ρL/A where ρ is resistivity, L is length, and A is cross-section. Power dissipated: P = VI = I²R = V²/R.
Worked Example
Problem: A 9 V battery drives current through a 270 Ω resistor. Find current and power.
- I = V/R = 9/270 = 0.033 A = 33 mA
- P = VI = 9 × 0.033 = 0.3 W
- Or P = V²/R = 81/270 = 0.3 W
Result: I = 33 mA; P = 0.3 W
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At A Glance
Category: Electromagnetism
Levels covered: High School, College, Masters, PhD
Best use: Start with the formula meaning, then move to the worked example and quiz so the equation turns into a tool instead of a memorised line.