Electricity from First Principles
Voltage & Energy
12 min · 2 worked examples · 3 questionsFree
Voltage is not a force and it does not flow. It is energy per unit charge.
After this lesson you can
- Explain why voltage is always between two points
- Say what a volt is in terms of energy and charge
- Explain why two boards must share a ground
Voltage is energy per charge
Voltage is the most commonly misunderstood quantity in electronics. It is not a force, it does not flow, and a component does not "use up" voltage in the way it uses current.
Voltage is defined as energy transferred per unit of charge:
V = E ÷ Q
where E is energy in joules and Q is charge in coulombs. So one volt means one joule of energy given to every coulomb of charge that passes. A 9 V battery gives each coulomb nine joules of energy to spend on its way round the circuit.
In the full lesson
- Voltage is energy per charge
- Potential difference
- The gravity analogy, and its limits
- Where the energy goes
Free with an account. Read it, work the examples, answer the questions, then build it in the simulator.