ElectricityDeep Dive

Parallel Resistance Shortcut (Two Resistors)

Part of Series & Parallel Circuits — GCSE Physics

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 is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. 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.

Topic position

Section 6 of 16

Practice

20 questions

Recall

30 flashcards

🧮 Parallel Resistance Shortcut (Two Resistors)

For exactly TWO resistors in parallel:

R_total = (R₁ × R₂) ÷ (R₁ + R₂)

"Product over sum" — much faster than the 1/R method!

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. The current is the same at all points
B. The current decreases after each component
C. The current is largest near the positive terminal
D. The current splits at each component

1 markfoundation

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.

2 marksstandard

Parallel Resistance Shortcut (Two Resistors)

🧮 Parallel Resistance Shortcut (Two Resistors)

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Practice Questions for Series & Parallel Circuits

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