This deep dive covers Parallel Resistance Shortcut (Two Resistors) within Series & Parallel Circuits for GCSE Physics. Revise Series & Parallel Circuits in Electricity for GCSE Physics with 20 exam-style questions and 30 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 6 of 16 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
🧮 Parallel Resistance Shortcut (Two Resistors)
For exactly TWO resistors in parallel:
Example: Two 10Ω resistors in parallel:
R = (10 × 10) ÷ (10 + 10) = 100 ÷ 20 = 5Ω
Special case: Two EQUAL resistors in parallel = half of one resistor
Quick check: Your answer must ALWAYS be less than the smallest resistor!
Practice questions for Series & Parallel Circuits
In a series circuit, what is true about the current at all points?
A student adds an extra lamp to a parallel circuit. Explain how this affects the total current from the supply and the brightness of the original lamps.