Series circuits · Year 10
In Year 10 you learn: adding resistances in series and sharing p.d. between resistors in series.
In a series circuit everything is in one loop. The same current flows everywhere, the supply's p.d. is shared between the components, and the resistances add up. If one part breaks, the whole loop stops.
Key facts
- In series, the bigger resistor gets the bigger share of the p.d.
Worked examples
Example 1
Two lamps are in series with a 9 V battery. The voltmeter across one lamp reads 5 V. What does the voltmeter across the other lamp read?
Answer: 4 V
Example 2
A second lamp is added in series with the first. What happens to the brightness, and why?
Answer: Both lamps are dimmer.
Example 3
Resistors of 3 Ω, 5 Ω and 4 Ω are in series. What is the total resistance?
Answer: 12 Ω
Example 4
A 6 V battery is connected to 10 Ω and 20 Ω resistors in series. What current flows?
Answer: 0.2 A
Example 5
A 12 V battery is connected to 4 Ω and 2 Ω resistors in series. Find the current and the p.d. across each resistor.
Answer: 2 A; 8 V and 4 V