Current Electricity Flashcards
Current
Q/t
An ammeter
A device that measures current and must be connected in series
Direct current
Always flows in one direction
Alternating current
Constantly changing direction
Voltmeter
Device that measures voltage and must be connect in parallel
Ohm
The unit of resistance. A conductor has a resistance of 1 ohm if a current of 1 A passes through it when a p.d. Of 1V is applied
Ohms law
The current flowing through a conductor is directly proportional to the p.d. across it, if the temp remains constant
Electrolysis
The passing of an electric current through a liquid causing a chemical reaction
A fuse
A safety device consisting of a piece of wire which melts when a current above a pre-set value passes through it
A miniature circuit breaker (mcb)
A safety device which breaks the circuit if it detects a current above above a pre set value
A residual current device (RCD)
A safety device that breaks the circuit if it detects a current difference between live and neutral above a pre set value
A radial circuit
Where a separate live and neutral wire are connected from the distribution box to an appliance which uses large current
A ring circuit
Where the live terminals of each socket are connected in a ring so that current can flow both ways
Bonding
A safety precaution whereby all metal pipes, taps and tanks are earthed
Kilowatt-hour
The amount of energy used by a 1000 W appliance in 1 hour
A semiconductor
A substance whose resistivity is between that of a good conductor and a good insulator
Holes
Positively charged gaps in a substance which are created when electrons break free from covalent bonds
Doping
The addition of impurities to a semi conductor to increase its conductivity
Intrinsic conduction
Occurs in a pure semiconductor when there is an equal number of electrons moving from - to + and holes moving in the opposite direction
Extrinsic conduction
An increased rate of conduction due to the addition of impurities
Thermistor
A semiconductor whose resistance decreases as temp increases
Light dependent resistor (LDR)
A semiconductor whose resistance decreases as light intensity increases
Ampere
The current flowing in two parallel conductors placed 1m apart in a vacuum that causes a force of 2x10^-7 Nm-1
N type semiconductor
Semiconductor in which electrons are the majority charge carriers
P type semiconductor
A semiconductor in which holes are the majority charge carriers
