Electricity Flashcards
(18 cards)
Electromotive force
The amount of energy supplied to each unit charge when a form of energy is transferred to electrical energy
Potential difference
Work done per unit charge
Current
Rate of flow of charge
Electromotive force equation
EMF = energy / charge
e=w/Q
Conventional current
Current flowing from positive to negative
Electron flow
Electrons flowing from negative to positive
Resistance
Potential difference across a component divided by current
Kirchoff’s first law
The sum of the current entering a junction is always equal to the current exiting the junction
Mean drift velocity
Average velocity of the electrons as they travel down the wire
What’s the value of an electrons charge
-1.6 x 10^-19
What is and how do you work out charge carrier density
Number of electrons in 1m^3
1/d^3
Conductors and insulators
Conductors - large no. of free conduction electrons per unit volume
Insulators - low no. of free conduction electrons (poor conductors)
Semi-conductors
Intermediate conduction properties , a value of n between conductors and insulators
n = (number density)
What happens when you increase temp on a semi-conductor
Electrical conductivity increases due to overcoming energy barrier
Coulomb
Amount of charge passing a point in a second when the current is 1A
Filament lamp behaviour
When current increases, electrons travel quicker leading to more collisions between electrons and the lattice structure. The ions in the lattice then vibrate as they have more kinetic energy reducing electrons which can get past. The resistance then increases as the temperature is increasing because of this.
The negative temperature coefficient thermistor
As temp increases, resistance decreases meaning current increases allowing other parts of the circuit to operate.
1 kilowatt-hour
Energy used by 1 kilowatt device in 1 hour when it is on.
