Charge of an electron
-1.6x10^-19 C
Define electric current
Electric current is rate of flow of charge (Q)
scalar
I = dQ/dt for constant current I=Q/t
Define Charge
Physical property of matter that causes it to experience force when placed in electric or magnetic field
Q=It for steady I
Q = C V c is a constant
Define electromotive force (emf)
The energy transferred from non-electrical forms to electrical forms per unit charge in driving a unit charge round a complete circuit
volts
V = W/Q W is energy transferred (J) , Q is charge (C)
sources of electrical energy
Define potential Difference
The energy transferred form electrical to non electrical forms per unit charge when a unit charge passes from o point to another
Difference between emf and pd
Emf exists as a property of the energy source regardless of whether a current is flowing in circuit
pd exists only if there is current flowing in circuit as it represents energy transfer due to motion of charged particles
emf refers to two points across the emf source
pd refers to any two points
Define Power
Power is define as rate of energy transfer due
watt
P = dW/dt W energy (J) , t in s
constant power P=W/t
P=QV/t = VI = I^2R = V^2/R
Define electric current
I = Q/t= nAvq
Q represents total charge
n represents number of charge per unit volume (m^-3)
q represents magnitude of charge of each mobile charge carrier (C)
v represents drift velocity v (average velocity in one direction along wire) (ms^-2)
A represents cross sectional area (m^2)
Represent AC or alternating voltage in graph
I=Io sin omega t
V=Vo sin omega t
omega = 2pif or 2pi/t
Define root mean square value of ac
is the value of steady direct current or voltage that dissipates heat energy in a resistor at same average rate as that is dissipated by alternating current or voltage
Power time graph
Po = Io^2 R = Io^2 R sin omega t = Po sin^2 omega t
Area under power time curve is energy, mean power <P> is half of peak power
For sinusoidal:
<p> = Po/2
Vrms = Vo/root 2
Irms = Io/root 2
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