# Physics Unit G482

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Unit G482 Electron Waves and Photons Definition Page

Conventional Current flows from Positive to negative, Whereas Electron Current flows from Negative to Positive

Charge (Q) = Current * Time

Definition of a Coulomb

For a Current of 1 Amp the charge past a point is 1 coulomb in a time of 1 second

Kirchoff's First Law

The sum of currents entering at a certain point is equal to the sum of currents leaving that same point

An Equation for current

I=A n e v

Where I= Current A= Cross-sectional Area n= Number density and e= Elemental charge

Definition of Mean Drift Velocity

The average distance travelled in unit time towards the positive terminal

Ohm's Law

For a metal conductor at constant temperature the Current is directly proportional to the Voltage

Negative Temperature Co-Efficient Resistor or Thermister

The resistance decreases with increasing temperature (an automatic air conditioner)

Resistivity= (Resistance * Cross-Sectional Area) /Length

Definition of Voltage/Potential Difference/ Electromotive force

Energy Transferred per unit charge

(Electromotive is gaining/ potential difference is losing)

Definition of the Volt

Volt= Joule per Coulomb

Definition of Power

The rate of energy transfer electrically Current*Voltage

Definition of the Kilowatt hour

The Energy Transfer by a 1 kilowatt device in 1 hour

Ammeters are connected in series and have a small resistance ideally 0  to take