13 Current of Electricity Flashcards
Number density, n
The number of particles per unit volume
Drift velocity, v
Average velocity at which charge carriers move through a conductor when there is electric current in the conductor
Direction of conventional current
positive terminal to negative terminal
Direction in which positive charges would move
Electric current, I
Rate of flow of charge through a cross-sectional area
I=Q/t
Derivation of I=nAvq
- I=Q/t
- Q=Nq (Total charge is number of charge carriers multiplied by charge of each carrier)
- N=nV (Number of charge carriers is the number density multiplied by the volume)
- V=Avt (Volume covered equals cross sectional area times distance covered, vt)
- I=nAvq
Coulomb, C
One coulomb is the amount of charge that flows through a given cross section of a circuit in one second when there is a constant current of one ampere
Potential difference, V
Amount of electrical energy converted to other forms of energy per unit charge moved between the two points
V=W/Q
Potential of earth/ground
V=0
Ohm’s Law
The current flowing in a conductor is directly proportional to the potential difference across it under constant physical conditions
Resistance, R
Ratio of the potential difference across a conductor to the current flowing through it
R=V/I
Resistivity, ρ
The proportionality constant between the dimensions of a specimen of a material and its resistance
R=ρL/A
Electromotive force, e.m.f.
Amount of energy transferred from non-electrical forms of energy to electrical energy per unit charge as the charge passes through a complete circuit
e.m.f. =W/Q
Terminal voltage, V
V=E-Ir
where r is the internal resistance of the battery and E is the e.m.f. provided by battery
Power, P
P=VI
Maximum Power Theorem
Max power when R=r
P(max) =E^2/4r
