Two cells: in series, in parallel, and one reversed
"Two cells: in series, in parallel, and one reversed" is a free, interactive Class 12 Physics simulation for NEET and JEE, built on the lesson "Cells in series and in parallel" in Current Electricity. Each dashed box is a real cell: an emf with its own internal resistance. Press Show the current, then switch between Series and Parallel and watch the equivalent emf and internal resistance. In series the emfs add (a reversed cell subtracts) and so do the internal resistances. In parallel the emf is a weighted average, r_eq is smaller than either r, and a weaker cell can end up being charged by the stronger one. JEE Main asked 65 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Cells in series and in parallel in Current Electricity. Change the values and watch what happens.
In JEE Main
42 shifts analysed
65 questions from Current Electricity across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT § "Cells in Series and in Parallel"
- Two cells in series (positive of one to negative of the next) behave like one cell of emf ε_eq = ε₁ + ε₂ and internal resistance r_eq = r₁ + r₂.
- If one cell in a series pair is reversed, its emf is subtracted: ε_eq = ε₁ − ε₂, while the internal resistances still add.
- For n identical cells in series: emf nε and internal resistance nr.
- Two cells in parallel (like terminals together) behave like one cell with ε_eq = (ε₁r₂ + ε₂r₁)/(r₁ + r₂) and r_eq = r₁r₂/(r₁ + r₂).
- The parallel formula can be written 1/r_eq = 1/r₁ + 1/r₂ and ε_eq/r_eq = ε₁/r₁ + ε₂/r₂; if one cell is reversed, its ε changes sign.
- For n identical cells in parallel: emf ε and internal resistance r/n.
- When two cells of unequal emf are joined in parallel with no external load, a current circulates between them, driven through the lower-emf cell by the higher-emf one.
Questions
3 answers
- What does the "Two cells: in series, in parallel, and one reversed" simulation show?
- Each dashed box is a real cell: an emf with its own internal resistance. Press Show the current, then switch between Series and Parallel and watch the equivalent emf and internal resistance.
- Does JEE Main ask questions from Current Electricity?
- Yes. JEE Main asked 65 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Cells in series and in parallel" in Current Electricity (Class 12 Physics).
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