Batteries and Cells
Chemical reactions push charge around a circuit.
About this topic
A cell converts chemical energy into electrical energy through a redox reaction between two different electrodes in an electrolyte; a battery is several cells connected together. The EMF is the voltage the cell gives with no current, and internal resistance causes the terminal voltage to drop under load: V = ε − Ir.
For example, a 1.5 V cell with an internal resistance of 0.5 ohm supplying 1 A has a terminal voltage of 1.5 − 0.5 = 1.0 V. This is why a nearly flat battery cannot power a bright torch even though it may still read close to its EMF on a voltmeter with no load.
Primary cells are used once, while rechargeable ones, like lithium-ion, reverse the reaction when charged. Batteries power phones, cars and increasingly grid storage, and a car battery can supply hundreds of amps for a short time to start the engine.
A battery does not store charge; it stores chemical energy and pushes existing charge round the circuit. The same number of electrons leave and return.
Key ideas
- emf is the energy per charge
- Internal resistance lowers terminal voltage
- Cells in series add voltage
Quick check
Use cases: where Batteries and Cells helps
- Homework: review the key idea behind Batteries and Cells before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Batteries and Cells without notes.
- Visual learning: play with the interactive lab to see how Batteries and Cells changes when you adjust its inputs.
- Teaching a friend: explain Batteries and Cells in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Batteries and Cells?
Chemical reactions push charge around a circuit.
What will I learn in Batteries and Cells?
emf is the energy per charge. Internal resistance lowers terminal voltage. Cells in series add voltage.
Is Batteries and Cells part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Batteries and Cells lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Batteries and Cells?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.