Science · Grades 10–12
Two parallel resistors
The equivalent resistance is less than either positive branch resistance.
The key idea
The equivalent resistance is less than either positive branch resistance.
R = R₁R₂/(R₁ + R₂)
Worked examples
Resistors of 12 Ω and 36 Ω are connected in parallel. Find the equivalent resistance in Ω as an exact fraction or integer.
12 × 36 / (12 + 36) = 9
9 Ω
Resistors of 34 Ω and 50 Ω are connected in parallel. Find the equivalent resistance in Ω as an exact fraction or integer.
34 × 50 / (34 + 50) = 425/21
425/21 Ω
Try it yourself
Resistors of 22 Ω and 42 Ω are connected in parallel. Find the equivalent resistance in Ω as an exact fraction or integer.
Resistors of 28 Ω and 23 Ω are connected in parallel. Find the equivalent resistance in Ω as an exact fraction or integer.
Check your understanding
Answers and marking notes
- 231/16 Ω
22 × 42 / (22 + 42) = 231/16
- 644/51 Ω
28 × 23 / (28 + 23) = 644/51
Further reading and review references
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Learning preview · teacher review required. Grade bands are approximate, not official curriculum alignment.