1.8 - Potential difference, electromotive force and
power
● ***Electromotive force (EMF): energy of any form (eg chemical, mechanical) per
unit charge converted into electrical energy ONLY; creates a potential difference (ie
voltage)
(SBA) energy per unit charge supplied to a circuit
W ( energy converted into∗electrical energy ONLY ∗[J ])
○ ***ε ( EMF [V ])=
Q(charge passing through a point [C ])
● ***Potential difference (PD): electrical energy per unit charge transferred between
any 2 points in a circuit
○ ***
W (work done−specifically∗electrical energy , converted into other forms∗[J ])
V (PD [V ])=
Q(charge passingthrough a point [C])
∆W W Q W Q
● P= , W =QV , = ×V , ∵ =P, =I , ∴ P=IV /¿
∆t t t t t
● P=IV , E=P ∆ t , E=VI ∆ t /¿
● EMF = “terminal potential difference”
Summary***
● EMF - Σenergy (total voltage from source) → electrical energy
PD - electrical energy ONLY (between ANY 2 points in circuit)
ε > V {given that r > 0)
1
power
● ***Electromotive force (EMF): energy of any form (eg chemical, mechanical) per
unit charge converted into electrical energy ONLY; creates a potential difference (ie
voltage)
(SBA) energy per unit charge supplied to a circuit
W ( energy converted into∗electrical energy ONLY ∗[J ])
○ ***ε ( EMF [V ])=
Q(charge passing through a point [C ])
● ***Potential difference (PD): electrical energy per unit charge transferred between
any 2 points in a circuit
○ ***
W (work done−specifically∗electrical energy , converted into other forms∗[J ])
V (PD [V ])=
Q(charge passingthrough a point [C])
∆W W Q W Q
● P= , W =QV , = ×V , ∵ =P, =I , ∴ P=IV /¿
∆t t t t t
● P=IV , E=P ∆ t , E=VI ∆ t /¿
● EMF = “terminal potential difference”
Summary***
● EMF - Σenergy (total voltage from source) → electrical energy
PD - electrical energy ONLY (between ANY 2 points in circuit)
ε > V {given that r > 0)
1
