Electromotive Force and
Potential Difference
Emf and P.d
You should be able to:
(a) define potential difference (p.d.);
(b) select and use the equation W = VQ;
(c) define the volt;
(d) describe how a voltmeter may be used to
determine the p.d. across a component;
(e) define electromotive force (e.m.f.) of a source
such as a cell or a power supply;
(f) describe the difference between e.m.f. and p.d in terms
of energy transfer
Circuit Symbols
• Draw any circuit symbol that you can
remember. ( there are 16 that you need to
know)
Emf and P.d
Emf and Potential difference
are about energy
Emf and P.d
Emf and P.d
Electromotive force is the energy
transferred per coulomb when one
other type of energy is converted into
electrical energy.
This tells us that emf :
• Is measured in joules per coulomb
• That it always deals with the supply of
electrical energy.
Emf and P.d
Emf and P.d
Potential difference is the electrical
energy transferred per coulomb when
electrical energy is converted into
another form of energy.
This tells us that pd :
• Is measured in joules per coulomb
• That it always deals with the use of electrical
energy.
Emf and P.d
V=W
Q
Emf and P.d
12V
Describe in terms
of energy what is
happening in this
circuit.
3V
9V