Required Practicals - Resistance Flashcards
What is the investigation of the resistance practical?
An investigation into the effect of changing the length of wire on resistance.
What is the apparatus of the resistance practical?
Connect a battery, switch and ammeter in series with a section of wire being connected in parallel with a voltmeter.
What is the equation for resistance?
Resistance = Voltage / current
How do we increase the length of wire in the resistance practical?
Attach the wire to a metre ruler using tape.
Connect the wire to the circuit using crocodile clips.
Only the part of the wire connected by the crocodile clips is connected to the circuit.
Move the crocodile clips further apart to increase length.
What is the relationship between resistance and the length of wire?
They are directly proportional.
What is the problem with the resistance and length graph?
There is a small resistance at length 0.
This resistance shouldn’t be there, it is a zero error.
What is a zero error?
A reading on a measuring instrument when the value should be zero.
What kind of error is a zero error?
A systematic error.
How do we deal with the zero error in the resistance practical?
Subtract the zero error from all of our readings.
Why does a zero error occur in the resistance practical?
The crocodile clip cannot easily be placed at the zero position on the ruler and there is some resistance caused by the contact between the crocodile clip and the wire.
Apart from zero error, what other problems occur in the resistance practical?
If the temperature of the wire increases, the resistance will also increase.
What can we do to reduce heating effects in the resistance practical?
Use a low p.d. to keep te current low and reduce heating.
Only turn on the current when taking a reading, turn off between readings.
How do we alter the resistance in a variable resistor?
We can control the potential difference across a lamp, the higher the resistance, the lower the power output.
