The formula for discovering the resistivity of a wire is Where: R is resistance P is the resistivity A is the cross-sectional area L is the length The variables included are the cross-sectional location (A), the length (L), the Resistance (r) and resistivity (P). The resistivity of every wire is constant So the altering variables are the resistance (r=v/I) where the resistance is The reliant variable. Keep the location constant. To determine how the modification in length affects the resistance, we outline a graph Of length versus resistance.
The resistance should be proportional to the Length, R? L (prediction) according to Ohms law i. e. there ought to be an
Boost in the resistance as the length increases- the longer the length, the Greater the resistance. DIAGRAM APPROACH: Set up the circuit as shown in the diagram above, start the experiment by taping The constantan wire of 100cm the has been determined to the metre rule. Make certain the wire is thoroughly tightened up at both ends of the metre rule then links The digital ammeter, and the voltmeter at last (the circuit need to have the ability to Function without it.
) As revealed on diagram above. Switch on the variable power Supply box. Tape the voltage and existing readings that are displayed on the digital screens Of the ammeter and voltmeter respectively.
Repeat the treatment using 8 Various lengths varying from 10cm to 80 cm. Then, repeat the exact same experiment Two more times to get an average. COMPUTING THE RESISTANCE The formula for determining the resistance is: Resistance = voltage/current (V/I) DETERMINING THE AREA Using a micrometer screw gauge, determine the size of the wire at 4 different Points and at ideal angles of each of these points and get an average. Then calculate the area With the formula A=? r Where r is radius=1/2 diameter A is area?
Is 22/7 DEVICES A digital ammeter of range 0-20 A, a digital voltmeter, which ranges from gative terminal blocks, readily available power supply box, A meter rule of 1– 1000mm graduation, a micrometer screw gauge and a Piece of constantan wire. SECURITY PREVENTATIVE MEASURES Do no touch the wire when the power supply box is switched on Do not cut yourself while cutting wire Be careful not to begin a fire by allowing the wire to overheat Be generally mindful and security conscious throughout the experiment After plotting the graph, calculate the gradient with the formula G= y2-y1 = y X2-x1 x After finding the gradient R=?
INITIAL EXPERIMENT Throughout the preliminary experiment, I observed that the resistance of a piece of wire is affected by the length and the Location the longer the wire the higher the resistance R? L The fatter the wire, the less the resistance R? L/A I observed that as the voltage increased, the current decreases, which implies that The current is inversely proportional to the voltage.
Infact as the wire is an Ohmic Conductor, the arise from the graph can be outlined an I-V graph. An Ohmic conductor Ought to yield a straight-line graph travelling through the origin. MAJOR SOURCES OF ERRORS Human mistakes Parallax errors Kinks and twists on the wire Change in diameter due to change in temperature ACTIONS PROPOSED TO MINIMISE MISTAKES Keep the location consistent as much as possible by trying to keep the temperature level Continuous at all times. This was done by changing the power supply box each Time you take a set of result to let it cool down for a while before changing it On to tape-record another set of results.
Likewise keep the area continuous by utilizing the same Piece of wire throughout the experiment. Try to prevent parallax mistake by utilizing a digital ammeter and voltmeter instead of a Major deflection ammeter and voltmeter. Make sure that the wire is carefully tightened up to both ends of the meter guideline and avoid Wires with loads of twists, which could modify the length and cross-sectional area Of the wire. To increase the decree of accuracy of the taped result and outlined graph, take 3 sets of results and compute the average, even when determining the area. Tape-record the diameter at a very little of four various indicate be able to measure.
The size of the wires properly as possible. Use terminal obstructs rather of crocodile clips because the crocodile clips kept Slipping out from each other and disturbing the circuit. These terminal blocks Make it much easier to link the circuit correctly, but on the other hand, they make it Difficult to measure the length precisely utilizing a meter rule, so utilize larger length So this inaccuracy is almost negligible. Finally try to avoid typical human mistakes as much as possible by being normally Mindful. The tape-recorded results of the voltage and present streaming through the circuit Length Current (A) 1 Present (A) 2.
Present (A) 3 Average current Volt. (V) 1 Volt. (V) 2 Volt. (V) 3 Typical voltage 1ANALYSING After plotting the graph of length versus the resistance, determine the gradient, m, With the formula At the end of my experiment, the resistivity of constantan wire Is 5. 75 x 10 ASSESSMENT: The abnormalities seen in my outcomes (graph) were as a result of approximations.
After I computed the resistance, I estimated the result in order to be able to place the numbers on my chart sheet and this affected my graph (gradient) because when I plotted the chart without estimating; I got a perfectly straight-line graph. Conclusion: I feel my experiment (useful) worked out and appropriated for the Job offered. This is revealed by the truth that I accomplished consistency and shows that This experiment can be both trusted and precise. My outcome is trustworthy as they are consistence with each other and I have handled to avoid making big errors.