physics paper 1 electricity Flashcards
what is work done
work done id the flow of electrons which allows energy to be transferred
why does current transfer energy to resistors
electrical current flow through metal conductor, when it flows through a component the electrons collide with atoms within it and transfer their electrical energy into other forms.
resistance tells us the potential difference/ voltage ( energy ) required to drive a current through a component.
the higher the resistance, the more energy transferred
current and potential difference are directly proportional (potential difference is the amount of energy transferred)
an ohmic conductor is a component that obeys ohms law which is that resistance does not change (stays constant) even if current changes.
diodes only allow the current through in one direction, this is because they have a very high resistance in the other direction.
the current cannot flow in a revere direction which is shown in the graph
diodes are very good for controlling the current in a circuit.
as current in forward direction increases so does potential difference
feature of LED
LED are very energy efficient and give off light as a current is passed through
what is the resistance in parallel
the total resistance in parallel is less that the resistance of the smallest individual resistor
effect wire length has on resistance
secure a wire to a metre ruler using sellotape. Then adjust the circuit to the wire using crocodile clips at a certain length. next repeat with different lengths.
wire length and resistance are directly proportional
problems with experiment:
systematic error/ zero error - crocodile clip cannot be placed exactly on the zero.
resistance caused by the contact between the wire and the clips
if the heat increases of the wire the resistance increases which affect the results.
solutions- use a low potential difference with keeps the current low reducing the heating of the wire
turn on the Current when taking a reading turn off the current between readings which will reduce heating effects
what are the uses of a thermistor
thermostats are appliances that regulate temperature. their resistance increases when temps are to low and resistance increase when temps are too high
how is a thermistor effective In controlling the heat of a computer
a computer has a built in fan with a thermostat, when the temp gets too hot the resistance of the thermistor decreases . as a result there is more potential difference for the fan to use so it can spin at a faster rate producing more air to cool it down. when the temp gets lower the resistance of thermostat increases there for there is less pd for the fan and the fan operates at a lower pd producing not much air
in an incubator it
how are light dependant resistors useful in phones
light dependant resistors can be used to detect light. If light intensity is low than resistance increases, if light intensity is higher resistance decreases
LDR resistance and potential difference is directly proportional if temperature is constant.
when the phone is near your ear there is less light there for increased resistance.There will be less electrical energy for the lamp as there is more pd to the resistor, as a result light will become dimmer.
when the phone is away for ear there is more light, resistance increase and there is more electrical energy for lamp. pd across lamp increases and the phone in light becomes brighter.
what is an ohm conductor
material that obeys ohms law meaning the resistance stays the same regardless of the p.d/ voltage and current passing through it.
describe the wire and resistance practical
sellotape a wire onto a rule. than using crocodile clips adjust the circuit to the wire at a certain length and then different lengths.
the longer the wire the higher the resistance/ wire and resistance are directly proportional.
errors with the experiment - zero systematic error- the crocodile clip creates a slight resistance even when length of the wire is zero. there for we will have to subtract the zero error from all reading.
if the temperature of the wire increase than the resistance can increase which will lead to inaccurate results, there for they should use a lower pd which will reduce current to reduce thermal energy heating unwire. or turn off the current in-between reading to avoid heating up.
