Parallel circuits · Year 10
In Year 10 you learn: current in each parallel branch.
In a parallel circuit there are branches. Each branch gets the full supply p.d., the branch currents add up to the total, and adding a branch lowers the total resistance. Homes are wired in parallel so each appliance works on its own.
Key facts
- Parallel: each branch has the full supply p.d.; currents add: I = I₁ + I₂ + …
- Adding another resistor in parallel lowers the total resistance, because it adds another path for the current.
Worked examples
Example 1
Two lamps are in parallel with a 6 V battery. What is the p.d. across each lamp?
Answer: 6 V
Example 2
Two identical lamps are in parallel. The ammeter next to the battery reads 1.5 A. What current flows through each lamp?
Answer: 0.75 A
Example 3
A 12 V battery is connected to 4 Ω and 6 Ω resistors in parallel. Find the current through each resistor and the battery current.
Answer: 3 A and 2 A; 5 A from the battery
Example 4
Adding another resistor in parallel does what to the total resistance?
Answer: It goes down.