H1 Physics 8867 · objective lesson
Potential difference and electromotive force
Both are energy per unit charge: e.m.f. describes energy supplied and p.d. describes energy transferred from electrical stores.
Repair the common break
Common misconception: Potential difference and e.m.f. are both forces.
Correct model: Both are energy per unit charge: e.m.f. describes energy supplied and p.d. describes energy transferred from electrical stores.
Worked transfer
A 1.5 V cell supplies 1.5 J per coulomb, while a 1.2 V component transfers 1.2 J per coulomb from electrical energy. Neither voltage is a force.
Guided practice
Explain why “Potential difference and e.m.f. are both forces.” fails. Then construct one example that correctly applies potential difference and electromotive force.
Independent practice
A source moves 24 C and supplies 144 J while 120 J is transferred in the external circuit. Determine its e.m.f. and terminal p.d.
Return to the recorded repair plan when the explanation and application are secure enough to re-test.