Electricity Flashcards
What is electric charge?
It is a fundamental property of matter that cannot be defined but existence and effect can be shown
What is a Coulomb?
1 Amp per second
Coulomb’s Law
t
Surface-density of a charge…
Increases with curvature
Electric field
=F/Q
=kQ/r^2
Electric field in a charged sphere=
0
Electric Potential
It is when a charge Q’ is moved between two points in an electric field
W= Change in EPE
V=kQ/r
Potential Difference (V)
The energy transferred in moving a positive charge from a lower potential to a higher one
V=W/Q
Causes charge to move
Current flows from high to low potential
Current
The rate of charge transfer
Amps
I=
Anev
Area of wire*Number of electrons*Charge of electrons*Average Drift Velocity
Current density, J=
I/A=nev
Define Resistance
Anything that impedes the flow of charge such as componenets or wires
R=V/I
In Ohms
Ohm’s Law
Constant temperature = Constant Resistance
Define Resisitivity
How strongly a material resists current flow
Direct Current DC
Majority of devices use this
Steady current flows in one diirection
EMF
Amount oof energy converted into electrical potential energy per unit charge
Voltage drop
Amount of electrical potential energy converted into other energy per unit charge
Krichoff’s First Law
The sum of the currents into a junction=The sum of the currents out of the junction
Kirchoff’s Second Law
In any circuit loop, the sum of the emfs=the sum of the pds
To find Internal resistance
EMF=I(R+r)
