Physics·Electricity and magnetism · NSSCO 5.2.2
Potential difference & e.m.f.
Narrated lesson · press play
Electricity is really about energy being carried by moving charge. In this lesson we meet two closely related ideas: potential difference (voltage) — the energy each unit of charge gives up in a component, V = W/Q — and electromotive force (e.m.f.) — the energy a source gives to each unit of charge, V = E/Q. We learn the volt, practise the calculations both ways, connect a voltmeter the correct way (in parallel), and finally see clearly how e.m.f. and p.d. differ.
What you'll learn in this lesson
By the end you should be able to (NSSCO Physics 5.2.2):
- Explain potential difference (p.d.) as the energy transferred per unit charge in a component, and recall and use V = W/Q
- State that both e.m.f. and p.d. are measured in volts, and that 1 volt = 1 joule per coulomb
- State and use the correct way to connect a voltmeter (in parallel, across a component)
- State that electromotive force (e.m.f.) is the energy given per unit charge by a source, and recall and use V = E/Q
- State that the potential difference between the terminals of a cell enables a current to flow
- State the difference between e.m.f. (total energy per charge from the source) and p.d. (work per charge in part of the circuit), and that they involve different energy changes
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