Science lesson plan · 8th grade (Year 9 in England) · 60 minutes
Current and voltage rules in series and parallel circuits
Electricity and magnetism
CCSS NGSS.MS-PS2-3CCSS NGSS.HS-PS3-5England: KS3 Physics: Electricity and electromagnetismEngland: GCSE Combined Science: Electricity (series and parallel)
Objective and success criteria
Students will: Current and voltage rules in series and parallel circuits.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Series and parallel circuits
Leads to: Total resistance of series and parallel networks
Materials: Circuit kits (cells, wires, bulbs), Circuit symbol cards, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).
Warm-up · 6 min
- Quick retrieval from earlier learning (Series and parallel circuits). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Two resistors of 17 Ω and 15 Ω are connected in series. What is their total resistance, in Ω? → 32 ΩPrompt: In series, resistances add.
- Adding more bulbs in parallel to a battery (each in its own branch) makes each bulb… (explode / stay about as bright as before / get much dimmer / go out) → stay about as bright as beforePrompt: Each branch gets the full battery voltage.
- Series and parallel: which statement is NOT true? (In a parallel circuit, the voltage across each branch is the same. / Voltmeters are connected in parallel. / In a series circuit, current is used up by each bulb. / In a series circuit, if one bulb breaks, the others go out.) → In a series circuit, current is used up by each bulb.Prompt: Is current used up in a circuit?
Hook · 6 min
- Show a circuit with a gap and ask why the bulb doesn't light.
- Share the objective: Current and voltage rules in series and parallel circuits. Read the success criteria together.
I do: model it · 12 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: Two lamps are connected in series to a 12 V battery. The voltage across the first lamp is 8 V. What is the voltage across the second lamp, in V?
- Step 1: 12 − 8 = 4
- Step 2: So the answer is: 4 V
- Answer: 4 V
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 12 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- Two lamps are connected in series to a 12 V battery. The voltage across the first lamp is 8 V. What is the voltage across the second lamp, in V? → 4 VPrompt: In series, the supply voltage is shared between components.
- A 0.8 A current leaves a battery and splits into two parallel branches. One branch carries 0.2 A. What current flows in the other branch, in A? → 0.6 APrompt: Current is not used up; it is shared between branches.
You do: independent practice · 17 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 7 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- In a series circuit with three lamps, one lamp breaks. What happens to the other two? (they go out / only one goes out / they get brighter / they stay the same) → they go outPrompt: A series circuit has just one loop.
- Two lamps are in parallel. The current through one branch is 0.3 A and through the other is 2 A. What current flows from the battery, in A? → 2.3 APrompt: In parallel, the current splits between branches.
Watch out for
- Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
- Remembering facts without the reason: ask "why?" and "what is the evidence?"
Support and stretch
Support
- Review first: Series and parallel circuits.
- Use concrete materials: circuit kits (cells, wires, bulbs).
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Move on to: Total resistance of series and parallel networks.
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-8.
Free lesson plan from eurekami.com/lesson-plan-builder