C2:Electricity Flashcards
what is p.d
a measure of how much energy is transferred by each coulomb of electron
what is current
rate of flow of charge (how many coulombs pass every second)
how do you calculate p.d
energy transferred/charge flow
how do you calculate current
charge/time
what is resistance
a measure of how much a component resist the flow of charge
what is a resistor
heats up when current flows through it
how are current and pd similar
directly proportional
how do you calculate resistance
(ohms law)
p.d/current
why does a larger current mean an increase in resistance
more heat means more movement of ions which causes more collisions which cause a higher resistance
whats a diode
only lets a current flow in one direction
what are the rules for a series circuit
total p.d is shared between components
current is the same
resistance is added together
what are the rules for a parallel circuit
p.d of battery = p.d of components
current split between
total resistance is less than the resistance of the smallest resistor
what is a thermistor
as temperature increases resistance decreases
power =
p.d x current
what does the neutral wire do (blue)
takes the current back to the source and stays ay 0v
what does the live wire do (brown)
averages out the p.d to 230v
changes between positive and negative potentials
what does the earth wire do (yellow and green)
safety wire which sends the current in the earth if the device becomes faulty
what is a fuse
melts and reduces the current
what do step up transformers do
increases voltage but decreases current to reduce the amount of power lost to heat
what does a step down transformer do
reduces voltage down to a safer and useable 230v for homes
why does resistance change for a metal
metals consists of a grid of ions surrounded by a sea of delocalised electron
They collide with ions and create heat
The higher the current the more frequent the collisions are which makes the ions vibrate more and makes it harder for electrons to flow
The resisitance has increased
what happens to resistance in a diode
low resisitance in forward direction
high resistance in reverse direction
whats the practical for resistance
metal wire with crocodile clips connected to it that has a circuit attached to it
move one clip along the wire
you should end up with a straight line through the origin
shows resistance and length of wire are directly proportional
what is a ldr
light intensity increases and resistance decreases
