Understanding Resistance and Ohm's Law
Part of Resistance & Ohm's Law — GCSE Physics
This deep dive covers Understanding Resistance and Ohm's Law within Resistance & Ohm's Law for GCSE Physics. Revise Resistance & Ohm's Law in Electricity for GCSE Physics with 14 exam-style questions and 30 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 2 of 16 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 2 of 16
Practice
14 questions
Recall
30 flashcards
📚 Understanding Resistance and Ohm's Law
Ohm's Law states that the voltage across a component is directly proportional to the current through it, provided temperature stays constant: V = I × R (Voltage in volts = Current in amps × Resistance in ohms). Rearranged: R = V ÷ I (to find resistance) and I = V ÷ R (to find current). A component is ohmic if it obeys this law at constant temperature (e.g. a resistor). A component is non-ohmic if resistance changes with conditions (e.g. a filament bulb — resistance increases with temperature; a diode — only conducts in one direction).
Resistance is a measure of how much a component opposes the flow of current.
Unit: Ohms (Ω) — named after Georg Ohm
- Higher resistance → lower current (for same voltage)
- Higher voltage → higher current (for same resistance)
- R = V / I (the most useful rearrangement)