BRAINCAKEElectricity
Revision notes for Electricity in OCR Physics A (H156). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Electric ChargeElectric charge is a physical property which can be either positive or negative.
- Electric CurrentThe flow of charged particles produces electric current.
- Millikan's Oil Drop ExperimentMillikan was able to calculate the charge on an electron.
- The Flow of Charge in Metals and ElectrolytesFor current to flow you need: • a complete circuit • charged particles (e.g. electrons). • and a source of potential difference The structure of a…
- Kirchoff's First Law and Conservation of ChargeAt any point in an electric current, the sum of currents into that point is equal to the sum of currents out of that point.
- Conductors and Semi-ConductorsMaterials can be classified into three groups according to their electrical properties.
- Current and Drift VelocityElectrons are moving around randomly in the metallic lattice at very high speed.
- Potential DifferenceThe potential difference is the work done per unit charge.
- Electromotive ForcePotential difference is used to describe when work is done by the charge carriers as they pass through components and transfer their energy from…
- The Electron GunThe electron gun is a device used to produce a narrow beam of electrons.
- ResistanceEach component resists the flow of charge carriers through it.
- Ohm's LawOhms Law states that for a metallic conductor kept at constant temperature the current in the conductor is directly proportional to the potential…
- Temperature and ResistanceIf the temperature is increased, the metal ions vibrate more.
- IV GraphsFixed resistors are designed to obey Ohm's law under normal changes of temperature when current flows.
- DiodesA diode only allows current to flow through it in one direction This property is important in electronic circuits as some components are affected by…
- ResistivityResistivity is used to describe an electrical property of a material.
- Temperature and Number DensityIf the temperature of a metal wire is increased, the positive ions vibrate more.
- The ThermistorA thermistor is a temperature dependent resistor.
- The Light Dependent ResistorA light dependent resistor is made of semi-conductor material in which the number density of charge carriers increases with the intensity of light.
- Electrical PowerElectrical power = potential difference × current.
- Electricity in the HomeAlthough the SI unit for energy is the joule energy transferred to homes is in the order of several hundreds of thousands of joules so the…
- Kirchoff's Second LawIn any circuit the sum of the electromotive forces is equal to the sum of the potential differences around a closed loop.
- Series CircuitsIn a series circuit there is only one path for the current to take from one terminal of the source through the components and back to the other…
- Parallel CircuitsA parallel circuit provides more than one path for the charges to flow.
- Combining ResistorsWith resistors in series the total resistance is equal to the sum of the resistances.
- Analysing CircuitsDifferent combinations of resistors in series and parallel are used to build more complex circuits.
- Internal ResistanceWork has to be done to move charge carriers through a power source so energy is lost when current flows through the source and the source gets hot.
- Potential Divider CircuitsA potential divider circuit can be used to divide the potential difference to any value up to the maximum provided by the power source.
- The PotentiometerInstead of using a pair of fixed resistors in series to split the potential difference one of the fixed resistors can be replaced with a variable…
- Sensing CircuitsA potential divider circuit with one of the resistors being a thermistors can be used as a temperature sensing circuit.