Electrical circuits Flashcards
alternating current
a current that continually changes direction (powered by generators)
ammeter
connected in a series cicruit and is used to measure amps
ampere
the unit of current
conductor
a material that allows electrical charge to flow easily
coulomb
the unit of charge
currents at a junction
the sum of the currents entering a junction must always equal the sum of the currents leaving it
diode
a component that only allows current to flow through in the forward direction. they have a very large resistance in the reverse direction
direct current
current flows in one direction only (powered by batteries and cells)
earthing
the removal of excess charge by providing a low resistance path for electrons to flow through
electric current
the rate of flow of electrical charge. I = Q/t
filament lamp
a light emitting component consisting of an enclosed metal filament. its resistance increases as the filaments temperature increases
fuse
a safety device consisting of a thin metal filament that melts and cuts off the power supply if there is a surge in current. They are connected to the live wire
insulator
a material that doesnt allow electrical charge to flow
light dependent resistor (LDR)
a light sensitive component whose resistance decreases as the light intensity increases
light emitting diode
a device that gives out light when a current flows through it. current can only flow through it in one direction, a a minimum voltage must be applied across it before it illuminates
live wire
the brown coloured wire that carries the alternating current from the supply in a mains power supply
ohm
a unit of resistance
ohms law
the current flowing through an ohmic conductor at constant temperature is directly proportional to the potiential difference across it (basically, current is directly proportional potential difference)
potential difference
the work done by a unit charge passing through a component in a circuit. V = IR
power
the rate at which an appliance transfers energy. P = IV or P = J/t
resistance
how difficult it for a charge to flow. R = V/I
resistors in parallel
the total resistance is less than the lowest individual resistance. Rt = (1/R1 + 1/R2)^-1
resistors in series
the total resistance is equal to the sum of the resistances of the individual resistors. Rt = R1 + R2
series
components connected in series have the same current passing through each component by share the total potential difference of the power supply
thermistor
a temperature dependent component, whose resistance increases as its temperature decreases
volt
the unit of potential difference. 1V = 1J/1C
Voltmeter
a device connected in parallel with a component to measure the potential difference across it
watt
the unit of power
EMF
electrical work done by a source in moving a unit charge around a complete circuit
Energy
the capacity of something to do work. J = Wt
joule
the unit of energy
Charge
a property of a body which experiences the electrostatic field force. Q = It
electrical work done formula
W = QV, work done = charge x potential difference
