Electricity

E.M.F.

The electrical energy given to charge carriers per unit charge

Internal resistance

The resistance of a source that resulted in energy loss as a charger passes through the source causing a difference between EMF and terminal p.d.

Tenner potentially difference

The p.d. supplied by an electrical power source

Potential divider equation

Equation here

Series rules

RT=R1+R2+…+Rn

IT=I1=I2=In

VT=V1+V2+…+Vn

Parallel rules

Resistance rule

IT=I1+I2+…+In

VT=V1=V2=Vn

Kirchhoff's second law

Sum of EMF=sum of p.d. in closed loop

Kirchhoff's first law

The sum of the current into a point = sum of the current out

Potential difference

The work done per unit charge

Current

The rate of flow of charge though a conductor

Ohmic conductor graph

Gradient change with resistance

Stepper → lower R

Shallower → higher R

Semiconductor graph

Zero current until a set p.d.

Filament bulb

Due to temperature changes not linear

But x=0 symmetrical

Superconductivity

Resistivity decreases to zero as temperature lowers

The critical temperature is the point at with the resistivity it above zero

Thermistor definition and uses

A negative temperature coefficient

T ∝ -R

Uses:

Thermostat

Measure temperature in electronics

Resistivity

The product of Resistance per unit length and the cross section area

ρ=RA/L

R∝L

R∝1/A