# Electricity

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• Created by: 14eb
• Created on: 29-11-19 11:03
• Electricity
• Potential Dividers
• Series
• By using two resistors, it is possible to divide a voltage and create a different voltage between them.
• V1/V2 = R1/R2
• Parallel
• Have to work out parallel resistance as R2 before using equation.
• V1/V2 = R1/R2
• Internal Resistance
• The amount of resistance present in the power supply of a circuit.
• Lost volts = Ir
• E=V+Ir
• E=I(r+R)
• Resistivity
• R=(pL)/A
• A measure of the resisting power of a specified material to the flow of an electric current.
• Electron Gun
• An electrical component in some vacuum tubes that produces a narow electron beam that has a precise kinetic energy.
• Computer monitors, televisions and cathode ray oscilloscopes.
• Drift Velocity
• The average velocity attained by charged particles in a material due to an electric field.
• I=Anev
• Ohm's Law
• V=IR
• The current through a conductor between two points is directly proportional to the voltage across the two points.
• Power
• V=IR
• W=QV
• P=IV
• Q=It
• The amount of energy changing form per second.
• Electromotive Force
• E=V+Ir
• E=I(r+R)
• The voltage when there is no current travelling around the circuit.
• V/I Characteristics
• Diode: No voltage until the threshold voltage, where it spikes up.
• Filament Lamp: A shallow S shape.
• Resistor: Directly proportional.
• Thermistor: Opposite S shape to filament lamp, increasing gradient.