Resistance cannot be measured, however you can calculate resistance with a formula ( voltage = current x resistance ).
To calculate resistance you need to know voltage and current when you find these two you divide them, then you know what resistance is.
Resistance increases whenever the current flows in a wire (when It heats up) it happens as a result of energy loss.
PREDICTION; I predict that that the longer the wire is the higher the resistance, because there will be more free atoms colliding with eachother.
VARIABLES
INDEPENDENT VARIABLES; alter length of wire
CONTROLLED VARIABLES; thickness of wire and temperature
DEPENDANT VARIABLE; voltage and current meausured. Voltmeter required to measure voltage, ammeter to measure current (amps). Both are needed to find resistance.
Voltage = current x resistance
APPARATUS; 100cm of nichrome wire, red and black leads, power pack, variable resistor, ammeter, crocodile clips, voltmeter.
USING RESULTS; A table of results will be present like this.
Then I will record the averages on a line graph, and put in a line of best fit like so
METHOD
- set up apparatus
- set the power pack to 2
- find the current, safely change it to the safe current pf 20.
- arrange the crocodile clips to 20cm on the nichrome wire.
- turn on power pack.
- record results (voltage and current).
- repeat this method for 40cm 60cm 80cm and 100cm
- Make sure you repeat the whole experiment again.
SAFETY PRECAUTIONS
Make sure the powerpack is set to 2 the whole time.
Make sure that all stools are pushed in.
Make sure you table is tidy before you start.
INTERPRETING
The longer the length of wire the more atoms and impurities in the wire are present therefore this means there are more collisions happening which increases the resistance.
EVALUATING
The method used seems to be the best way of performing the investigation, although if it was to be repeated the following improvements would be made:
• Carry out the experiment for more lengths, such as 10cm, 30cm etc. This would help to obtain a more reliable set of results.
The evidence obtained was reliable, however like I previously said I could have obtained a more reliable set of results by carrying out the experiment for more lengths of wire to reinforce my point that the longer the length of wire the greater the resistance is.
Taking all this into account, the results and evidence obtained is sufficient enough to support the conclusion that the longer the length of wire, the more atoms and impurities in the wire are present therefore meaning the resistance is greater.
