My chosen factor:
I intend to investigate how the length of a wire affects the overall resistance. I will do this by measuring the wire and making a note of the results, then I will analyse the results and come up with a conclusion. I need to fix the above factors so that they do not give me misleading or anonymous results. I will set the distance carefully using a metre rule and always measure from the inside part of the crocodile clip to the other crocodile clip.
Fixing the other factors:
-I will keep the temperature the same by turning the power off after each reading for a long enough time for it to cool down to its original temperature or do the readings straight after to each other not allowing for the temperature to increase.
-I will need to change the length of the wire as this is the factor I am investigating.
-The diameter of the wire will stay constant as I am using the same wire throughout.
-Again, the material of the wire will be the same as I am using the same wire throughout.
-I will ensure that I use a fully functional, clean and new wire to make sure it has no impurities in it, visually you can see if the wire has imperfections in it.
Prediction:
I predict that the longer the piece of wire, the greater the resistance as the electrons collide into more obstructions, if they are in the wire for a longer time and more collisions therefore means more energy is needed to get current through. If there is a longer length of wire there will be more ions so as the length goes up so will the resistance as the number of ions is increasing making it harder for electrons to travel, this is a direct proportional relationship, meaning as one aspect goes up so does the other. If I were to double the resistance I should expect half the resistance.. Essentially the more collisions that occur means the higher the resistance. The longer the piece of wire, the higher the current and voltage. I must not leave the apparatus on for too long or do too many experiments at one time otherwise the wire will get too hot, temperature affects resistance
Preliminary work:
I carried out a trial experiment prior to writing.
I set up a circuit using:
- A power pack (Wier)
- A voltmeter
- An ammeter
- A metre rule
- A metal wire
- A resistor
I used wires and crocodile clips to connect everything together. The voltmeter was connected in parallel to the metal wire and the ruler. The ammeter was connected in series and the variable resistor was also connected in series, which controls the current. Doing a trial experiment allows me to decide on a suitable voltmeter and ammeter to use in my experiment, it also helps to find an appropriate range of lengths to use; I will use a range of 10.0cm to 100.0cm with intervals of 10.0cm
I will use an ammeter that measures up to
I will use a voltmeter that measures up to
Diagram:
Safety:
-The wire gets hot so I won’t leave the power pack on for long.
-I will avoid touching the wire.
-I will make sure all wires are neatly placed so no one will trip on it as I will be plugging the Wier into a mains socket.
-The Wier will get hot after a while so I will avoid touching it
-Make sure no one will be in danger from the placement of the ruler, I will keep it on my bench not sticking out.
-Communicate with others when going to get apparatus so others are aware where you are and what space you need to be allocated.
Fair Test Table:
Method:
1) I will set up my apparatus as shown in the diagram above.
2) I will measure 10cm from crocodile clip to crocodile clip
3) I will switch on the power supply long enough for me to measure and take down the voltage and current. I will calculate the resistance using this equation:
Resistance= voltage
---------
current
I worked this out from Ohms Law, V / IxR.
4) I will carry out the above method for a range of lengths from 10cm to 100cm with an interval of 10cm. I will repeat experiment a minimum of five times to check for consistency, reliability and anonymous results.
I used wires and crocodile clips to connect everything together. The voltmeter was connected in parallel to the metal wire and the ruler. The ammeter was connected in series and the resistor was also connected in series, which controlled the current.
