This common misconceptions covers Common Misconceptions within Resistance & Ohm's Law for GCSE Physics. Revise Resistance & Ohm's Law in Electricity for GCSE Physics with 16 exam-style questions and 30 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 11 of 16 in this topic. Use this common misconceptions to connect the idea to the wider topic before moving on to questions and flashcards.
⚠️ Common Misconceptions
Misconception 1: "All components obey Ohm's Law"
Only ohmic conductors (like fixed resistors at constant temperature) obey Ohm's Law. Components like filament lamps, diodes, thermistors, and LDRs are non-ohmic — their resistance changes with conditions. Ohm's Law states that V ∝ I only when resistance is constant.
Misconception 2: "A thicker wire always has more resistance"
This is the opposite of the truth. A thicker wire has a larger cross-sectional area, which means more pathways for electrons to travel side-by-side. This reduces resistance. Think of a wider road allowing more traffic — it decreases congestion (resistance), not increases it.
Misconception 3: "Resistance of a metal decreases when it gets hotter"
For metals, the opposite is true: resistance increases with temperature (greater ionic vibration causes more electron collisions). It is thermistors and semiconductors that show decreasing resistance with increasing temperature. Students often confuse these two opposite behaviours.
Practice questions for Resistance & Ohm's Law
Which of the following best describes electrical resistance?
Explain what is meant by an ohmic conductor.