Parallel circuits · Year 11
In Year 11 you get fluent with: 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
- Adding another resistor in parallel lowers the total resistance, because it adds another path for the current.
Worked examples
Example 1
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 2
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 3
Adding another resistor in parallel does what to the total resistance?
Answer: It goes down.
Example 4
Resistors of 10 Ω and 40 Ω are in parallel across 8 V. Which one carries more current, and how much more?
Answer: the 10 Ω resistor; 0.6 A more