click below
click below
Normal Size Small Size show me how
Current Electricity
LC Cert Physics
Term | Definition |
---|---|
Potential Difference | This is the work done bringing a charge of + 1 C from one point to another. |
The Volt | The potential difference between two points is 1 volt if 1 joule of work is done when 1 coulomb is brought from one point to the other. |
Work | (Charge)(Voltage) |
Capacitance | Ratio of the charge on a conductor to its potential |
The Farad | A conductor has a capacitance of 1 farad if placing a charge of 1 C on it raises its potential by 1 volt. |
Electric Current | Flow of electric charge. |
Charge | (Current)(time) |
Ammeter | Instrument used to measure current. |
Voltmeter | Instrument used to measure voltage. |
Ohmmeter | Instrument used to measure resistance. |
Galvanometer | Sensitive ammeter measuring microamps. Also known as a microammeter. |
Faradmeter | Instrument used to measure capacitance. |
EMF | Electromotive force is the voltage applied to a circuit. |
Resistance | Ratio of potential difference to current flowing through a conductor |
The Ohm | A conductor has a resistance of 1 ohm if the current through it is 1 ampere when the potential difference across it is 1 volt. |
Ohm' s Law | Potential difference is directly proportional to current flowing through certain conductors at a constant temperature. |
Resistivity | (resistance)(Area)/ (length) |
Joule's Law | States that the rate at which heat is produced in a conductor is directly proportional to the square of the current provided. resistance is constant. |
Anode | Electrode connected to positive terminal. |
Cathode | Electrode connected to the negative terminal. |
Inactive electrodes | Electrodes that do not take part in a chemical reaction. e.g. platinum electrodes in electrolysis of water |
Active electrodes | Electrodes that do take part in the chemical reaction. e.g. copper electrodes in copper sulphate solution |
Electrolysis | When an electric current passes through a liquid causing a chemical reaction. |
Ion | An atom or a molecule that has lost or gained one or more electrons. |
Kilowatt hour | The amount of energy used by a 1000 W appliance. |
Fuse | A piece of wire that melts when a current of a certain size passes through it. It is always connected to the live wire. Used as a safety device to prevent overheating in a circuit and a potential fire. |
MCB | Minature circuit breaker is a safety device that trips when a current larger than a pre-set value flows through the circuit. Faster than a fuse and can be reset. |
RCD | Residual current device operates by detecting a difference of current between the live and the neutral wire. This difference is normally 30 mA and causes the RCD to trip preventing electrocution. Can be reset. |
Radial Circuit | Appliances that take a large current have a separate live and neutral wire coming from the distribution box and has its own fuse. e.g. cooker, electric shower |
Ring Circuit | Live terminal of the sockets connected together. Each ring circuit has a fuse in its live. |
Bonding | All metal water pipes, metal taps etc must be connected to the earth. Safety feature to prevent electrocution. |
Earthing | The process in which the instantaneous discharge of the electrical energy takes place by transferring charges directly to the earth through low resistance wire. i.e. provide a path of least resistance. |