Electricity

• Current is measured in amps (A)
• Current is the flow of electrical charge
• Charge will only flow in a circuit if there is a potential difference.
• The greater the pd, the more current flows through the component.
• Potential difference is the driving force that pushes the current around, measured in volts (V).
• Charge flow=Current X Time

  (Q=IT)
• Energy transferred by an appliance per second is called power.
• Power = Current x Potential Difference (W=VI)
• Resistance is the opposition to the flow of electric current, measured in ohms (Ω).
• Potential Difference=Current X Resistance

  (V=AR)
• Resistance of ohmic conductors doesn't change with the current.
• When charge flows through a filament lamp, it transfers some energy to the thermal energy store. Resistance increases with temperature.

  
• In diodes, resistance depends on the direction of the current.

  
• Light dependent resistors are dependent on the intensity of light.

  In bright lights, resistance falls.

  In darkness, resistance is highest.
• Thermistors are dependent on temperature.

  In hot conditions, resistance drops.

  In cool conditions, resistance goes up.
• In series circuits, different components are connected from the positive and negative of the power supply.
• In parallel circuits, each component is separately connected to positive and negative of the power supply.
• The total resistance of two or more components in series is equal to the sum of their individual resistances.
• In series circuits the total pd of the supply is shared between the various components. In parallel all components get the full source of pd.
• There is a bigger pd when more cells are in series as the pd is shared between them.
• If you have two resistors in parallel, their total resistance is less than the resistance of the smallest of the two.
• When there are multiple lamps in parallel, they will be brighter because they share the same current but receive the full voltage.