Circuits
Batteries in series
Two EMFs add up in series
Batteries in series — interactive Circuits simulation. Two EMFs add up in series Free browser-based virtual physics lab with live SI measurements and a guided tutorial.
Batteries in series
Ideal batteries in series add their EMFs, increasing the voltage available to the load.
Two 6 V cells in series behave like one 12 V source. The same resistor then draws twice the current of a single cell.
- ε_total = ε₁ + ε₂
- I = ε_total / R
Investigation brief
Plan the question before you open the lab
The brief mirrors the prerendered page: driving question, competing predictions, variable roles, governing laws, setup, analysis and extension prompts remain visible and in this order.
Driving question
Two 6 V batteries are connected in series (same orientation) driving a single resistor. Does the circuit behave like one 6 V source or like a bigger combined source?
Predictions to weigh
- The EMFs add — the circuit behaves like a single 12 V source.
- The circuit behaves like the average, 6 V.
- The batteries cancel out, driving no current.
Variable roles
What you set:
- Battery b2 EMF (V)
What you measure:
- Total EMF (V)
- Current I (A)
How the investigation runs
- Open the series-batteries preset and press Reset. b1 = 6 V is fixed; R1 = 100 Ω is fixed.
- Enable the current readout on R1.
- Set b2's EMF for each trial and record the circuit current.
Governing equation
Series EMF Sources — V = I·R
Batteries wired in series with matching polarity add their EMFs directly: EMF_total = b1 + b2. The single resulting loop current is then I = EMF_total/R, by Ohm's law applied to the combined source.
What the printable worksheet asks students to work out
- For one trial, compute total EMF = b1 + b2 using b1 = 6 V, then I = EMF_total/R1 using R1 = 100 Ω. Compare to the table.
- Explain why two batteries wired in the same orientation (positive terminal to negative terminal) add their EMFs, the same way series resistances add.
Where this shows up beyond the lab
- If b2 were flipped (wired backward), its EMF would subtract instead of add: total EMF = b1 − b2. Explain why reversing one battery in a series pair works against the other.
- A flashlight using 2 AA batteries (1.5 V each) in series runs its bulb at 3 V. Using this experiment's relationship, explain why adding a third AA battery in series would make the bulb burn out faster.
- AP Physics 2 — Unit 11: Electric Circuits
- AP Physics C: Electricity and Magnetism — Unit 11: Electric Circuits
- IB Physics — B.5 Current and circuits
- General High School Physics — Electricity & DC circuits
- NGSS High School Physics — Electric current and magnetic fields
- Welcome to Series Batteries
- Select the resistor
- Press Play
- EMFs add
- Open the Properties panel
- You did it!
Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.