Electricity

• charge is the measure of the number of electrons, the unit for charge is the Coulomb
• Current is the measure of the rate of flow of charge, 1 Ampere is equivalent to 1 Coulomb of charge per second
• potential difference is a measure of energy transferred by the charge as it passes through a component
• resistance is a property of all materials that restricts the flow of electrical currents
• direct current - cells and batteries supply electricity in a single direction, the electrons flow in the same direction
• alternating current - current that changes direction at regular intervals
• in the UK the current changes direction at a frequency of 50Hz
• electricity supplied to our homes is called mains electricity, it is alternating current and has an average potential difference of 230V
• the electrical power of a device is equal to the rate at which it transfers energy
• the fuse is a safety feature that contains a fine wire that breaks the circuit if the current exceeds the rated value
• a series circuit is where the components are connected in a single loop
• the current in a series circuit is the same in all components
• the potential difference in a series circuit is shared between the components
• a parallel circuit is one where the current has a different path to take
• the current in a parallel circuit are shared across components
• the potential difference in a parallel circuit remains the same across each branch
• the resistance in series circuits is the sum of all the resistances
• the resistance in a parallel circuit is less than the resistance of the smallest of the resistors
• a light-dependent resistor (LDR) depends on light intensity, at low light levels the LDR has a high resistance, as the light intensity increases the resistance decreases
• a thermistor depends on temperature. At low temperatures, the resistance is high and as the temperature increases the resistance decreases