Series and parallel circuits
In a series circuit everything is in one loop, so the current is the same everywhere. In a parallel circuit there are branches, and each branch gets the full voltage.
Key facts
- Series: same current everywhere; voltages add up; resistances add.
- Parallel: branch currents add up to the total; each branch has the same voltage.
- Parallel resistors: 1/R = 1/R₁ + 1/R₂, so the total is less than the smallest.
- Homes are wired in parallel so each appliance works on its own.
Worked examples
Example 1
Two 6 Ω resistors are connected in series, then in parallel. Find the total resistance each way.
- Series: 6 + 6 = 12 Ω.
- Parallel: 1/R = 1/6 + 1/6 = 1/3 R = 3 Ω
Answer: 12 Ω and 3 Ω
Example 2
In a parallel circuit the cell supplies 1.5 A. One branch takes 0.6 A. How much does the other take?
- 1.5 − 0.6 = 0.9 A
Answer: 0.9 A