17 current of electricity Flashcards
Definition
Current
The rate of flow of charge.
Unit: Ampere
Formula
Current
I = Q/ t
t = time (s)
Conventional Current
Short end to long end of battery
Electron Flow
Long end to short end of battery
Definition
Electromotive Force (e.m.f.)
The work done by the source in driving a unit charge around a complete circuit.
Unit: Volt (V)/ Joule per Coulomb (J/C)
Formula
Electromotive Force (e.m.f.)
E = W/Q
W = work done
Q= charge
Definition
Potential Difference (p.d.)
The work done by the source in driving a unit charge through a component.
Formula
Potential Difference (p.d.)
E = W/Q
W = work done
Q = charge
Definition
Resistance
The ratio of Potential Difference across the component to the Current flowing through it.
Unit: Ohms (Ω)
Formula
Resistance
R = V/I
Formula
Resistance
in a Wire
R = (ρl)/A
l = length of wire
A = cross-sectional area of wire
ρ = density of wire
Unit: Ohm-metre (Ω/m)
Definition
Ohm’s Law
The current through a metallic conductor is directly proportional to the potential difference across the ends of the conductor, provided that temperature and other physical conditions remain constant.
