S4.12.2 For the adult

Potential difference

Ana's torch cell is marked 1.5 V and her radio battery is marked 9 V. What are those volts measuring?

What this chapter teaches

Potential difference is the energy transferred for each coulomb of charge, V = E ÷ Q, in volts, where 1 V is 1 J/C. An ammeter goes in series and reads the current through a part. A voltmeter goes in parallel and reads the p.d. across a part.

Three questions to ask

There is no one right wording. Listen for the idea.

  1. What does it mean to say a lamp has a p.d. of 3 V across it?
  2. Where does a voltmeter go, where does an ammeter go, and what goes wrong if they are swapped?
  3. A 12 V battery moves 5 C of charge. How much energy does it transfer, and how did you work it out?

After the chapter, the learner can

  • Explain potential difference as energy transferred per unit of charge
  • Connect a voltmeter in parallel and an ammeter in series

What they copy into their notebook

p.d. is energy for each coulomb. V = E ÷ Q, so E = QV. 1 V = 1 J/C. Ammeter in series, voltmeter in parallel, across the part.

Back to the chapter