Definitions

• Emf is the work done to charge carries as they pass through components like cells and batteries
• Pd is the work done by charge carries as they pass through components like bulbs and resistors
• 1v = 1J per 1C
• Reflection occurs when a wave changes direction at a boundary between two different media but remaining in one medium
• Refraction occurs when a wave changes direction as it changes speed when it passes from one medium to another
• Conductors:

  • Materials that allow the flow of electrical charge
  • Good conductors have a larger amount of free charge carriers to carry a current
• Conservation of Charge:

  • The total charge in a system cannot change
• Conventional Current:

  • The flow from positive to negative, used to describe the direction of current in a circuit
• Coulomb:

  • The unit of charge
• Electric Current:

  • The rate of flow of charge in a circuit
• Electrolytes:

  • Substances that contain ions that act as charge carriers and allow current to flow when dissolved in a solution
• Electron Flow:

  • The opposite direction to conventional current flow
  • Electrons flow from negative to positive
• Elementary Charge:

  • The smallest possible charge, equal to the charge of an electron
• Insulators:

  • Materials that have no free charge carriers and do not allow the flow of electrical charge
• Kirchhoff's First Law:

  • The total current entering a junction must equal the total current leaving it
• Mean Drift Velocity:

  • The average velocity of an electron passing through an object
  • Proportional to the current, and inversely proportional to the number of charge carriers and the cross-sectional area of the object
• Quantisation of Charge:

  • Charge can only exist in discrete packets of multiples of the elementary charge
• Semiconductors:

  • Materials that can change their number of charge carriers and ability to conduct electricity
  • Examples include light-dependent resistors and thermistors
• Diode:

  • A component that allows current through in one direction only
  • Has a threshold voltage (typically 0.6 V) above which current can flow
• Electromotive Force:

  • The energy supplied by a source per unit charge passing through the source, measured in volts
• Filament Lamp:

  • A bulb consisting of a metal filament that heats up and glows to produce light
  • Resistance increases as the filament temperature increases
• 1. V Characteristics:

  • Plots of current against voltage that show how different components behave
• Kilowatt-Hour:

  • A unit of electrical energy used to measure domestic power consumption
• Light-Dependent Resistor:

  • A light-sensitive semiconductor whose resistance increases when light intensity decreases
• Negative Temperature Coefficient Thermistor:

  • A thermistor whose resistance decreases as temperature increases
• Ohm:

  • The unit of resistance
• Ohmic Conductor:

  • A conductor for which the current flow is directly proportional to the potential difference across it under constant physical conditions
• Ohm’s Law:

  • The current and potential difference through an ohmic conductor held under constant physical conditions are directly proportional, with resistance as the constant of proportionality
• Potential Difference:

  • The difference in electrical potential between two points in a circuit
  • Work done per coulomb to move a charge from lower to higher potential point, measured in volts
• Power:

  • The rate of energy transfer in a circuit
  • Calculated as the product of current and potential difference, measured in watts
• Resistance:

  • A measure of how difficult it is for current to flow through a material
• Resistivity:

  • A measure of how difficult it is for charge to travel through a material
  • Proportional to the object’s resistance and cross-sectional area, inversely proportional to the object’s length, measured in Ohm metres
• Resistor:

  • A device with fixed resistance that follows Ohm’s law
• Volt:

  • The unit of potential difference
• Conservation of Energy:

  • Energy cannot be created or destroyed, only transferred into different forms
• Internal Resistance:

  • The resistance to the flow of charge within a source, resulting in energy dissipation within the source
• Kirchhoff's Second Law:

  • The sum of voltages in any closed loop must equal zero
• Lost Volts:

  • The difference between a source’s emf and terminal voltage, equal to the potential difference across the source’s internal resistance
• Parallel Circuit:

  • Components connected across each other in separate loops
• Potential Divider:

  • A method of splitting potential difference by connecting two resistors in series, split in the ratio of their resistances