S4.12.5 For the adult
Series circuits
Tariq puts a second lamp in the same loop, and both lamps glow more dimly than one did. Why?
What this chapter teaches
In a series circuit the current is the same everywhere, the resistances add, and the p.d.s add up to the p.d. of the supply. A bigger resistance takes a bigger share of the p.d. If one part breaks, the loop is broken and everything stops.
Three questions to ask
There is no one right wording. Listen for the idea.
- Two resistors of 10 Ω and 30 Ω are in series. What is the total resistance, and why does it add?
- A 12 V battery drives a current through those two resistors. How would you find the p.d. across each?
- Why do two lamps in series glow less brightly than one lamp alone?
After the chapter, the learner can
- Calculate total resistance in series
- Explain how voltage is shared in a series circuit
What they copy into their notebook
Series: one path. Same current everywhere. R = R₁ + R₂. The p.d.s add up to the supply. The bigger resistor takes the bigger share. One break stops all.