electricity - resistance and resisters Flashcards
what does resistance tell us
the potential difference required to drive a current through a component
what is the difference between low and high resistance
high resistance takes more energy to drive the current through the component
equation for resistance
resistance = potential difference / current
what is a resister used for
to add resistance into a circuit
give an example of when you would use a resister
to dim a lamp
what is the relationship between current and resistance
they are directly proportional
what is an ohmic resister
when the resistance is constant and doesnt change when we increase the current
when will the resistant stay constant
if the temperature is constant
why are filament lamps being fazed out
they aren’t very efficient
what does the word filament mean
a very thin wire
what is the relationship like between a filament lamp and potential difference
the current though a filament lamp id not directly proportional to potential difference
as temperature increases what happens to the resistance
as temperature increases the resistance increases
what are resisters like in a series circuit
they add together - the current has to pas though each resister to turn it
what is equivalent distance
when you could replace two resisters (100v and 50v) for just 1 resider (150v)
what are resisters like in a parallel circuit
the total resistance of two resisters in parallel is less then the resistance of the smallest individual resister
what happens to a light-dependent resistor (LDR) in dark conditions vs light conditions
in dark conditions the LDR has a high resistance
in light conditions it has a very low resistance
give an example of the use of an LDR
in a phone
e.g. when taking a call, your phone screen will turn off so it saves battery
for this required practical what equipment is required
a battery, ammeter, voltmeter and length of wire
what is step 1 in this practical
tape the wire onto a meter ruler stick, and connect it to the rest of the circuit using crocodile clips
how much of the wire is included in the circuit
only the amount between the crocodile clips
what will you change about the wire and how
you can change the length of the wire by simply moving the crocodile clips further or closer together
after measuring the resistance of the changing wire length, what does the graph look like and what does this mean
it is a straight line showing us that the resistance of the wire is directly proportional to the length of the wire
what is a zero error
a reading on a measuring instrument when the value should be zero
how can we reduce a systematic error
we can’t
