Electric Circuits

• A cell is a store of chemical energy.
• A battery consists of two or more cells in series.
• A switch can break or join the circuit, turning current on or off.
• A lamp lights when current is flowing.
• An ammeter measures current.
• A voltmeter measures the size of the potential difference.
• Variable resistors allow current to be varied.
• A fuse melts or blows when current is greater than its current rating.
• A diode only allows current to flow in one direction.
• An LED emits light when a current flows through it.
• Another use of LED lights is as an indicator to show when an appliance is switched on.
• The resistance of an LDR in bright light is low, while in low intensity it is high.
• The resistance of a thermistor decreases as the temperature rises.
• In a series circuit, components have the same current through each component and the power supply's potential difference is shared between components.
• In a parallel circuit, potential difference across each component is the same and total current through the circuit is the sum of current through separate components.
• Total resistance of two resistors in parallel is less than the resistance of the smaller individual resistor.
• Direct current flows in one direction through resistors.
• Alternating current flows first one way then other through a resistor.
• Alternating current makes up for time with low power.
• Potential difference between live and earth wire is 5 230 V.
• Electrostatic force is a contact force.
• Live and neutral wires carry current to and from an electrical appliance.
• Voltage of neutral wire is close to 0V.
• Electrical appliances should be cased ones with a metal case and earth wire connected to its metal case.
• Low current wastes less energy when carried.
• The three core cables that connect to mains are live wire, neutral wire, and earth wire.
• Charged objects exert noticeable forces on each other when brought close together.
• Frequency of mains supply is 50 Hz.
• When static electricity is produced, a spark is produced, which is the potential difference made by positive and negative charges.
• Potential difference of mains supply is 230V.
• Electrical power is transferred through the national grid, a system of cables and transformers that links power stations to consumers.
• The direction of electric field is the same as the direction of force on a positively charged object.
• Earth wire carries current if there is a fault.
• Any contact between live wire and earth wire is dangerous because a large current passes to earth which could start a fire.
• Static electricity is produced by rubbing some insulating materials together.
• High potential difference lowers current.
• When a person touches live wire, current passes through them to earth, causing a painful shock.
• Potential difference of supply rises to make up for the time when potential difference is close to zero.
• Live wire carries alternating potential difference from mains supply.
• A charged object creates an electric field around itself, and the field is strongest close to the object.