An Experiment To Find The Resistivity Of — страница 2
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available digital ammeters that had a current range from 0-1A. I chose to keep the current passing through the circuit constant by passing a small current of 0.2A throughout the whole experiment. This maintained the temperature of the wires in the circuit because large currents would heat up the wires thus damaging the circuit and affecting the resistivity of nichrome. Voltmeter: – I chose to use a digital voltmeter of range 0-5V instead of a full scale deflection voltmeter to avoid parallax error when recording the voltage readings. It would have been ideal for me to have used a digital voltmeter of range 0-2V but this type of voltmeter was unavailable. The only digital voltmeters that were available for me to use had either a voltage range from 0-1V or from 0-5V or from 0-20V.When I did a preliminary experiment I found that the voltage readings that I recorded ranged from 0-1.9V and so the digital voltmeter with a range of 0-5V was the most ideal one to use. I recorded 3 sets of voltage readings and decided to take an average voltage reading for each length to ensure a greater accuracy in the obtained results and in the plotted graph. Length of the wire: – At the beginning when I did a preliminary experiment I was using crocodile clips instead of terminal blocks to connect the wire to the circuit. Although the crocodile clips made it easier for me to measure the length of the wire however I found it very difficult to keep the wires in these clips since it kept slipping out so the wire wouldn´t get connected successfully to the circuit. I therefore decided to use terminal blocks because even though these blocks make it more difficult for the wire to be measured accurately using a meter ruler, this can be overcome by using large wire lengths so that the inaccuracy in measuring its length will become very tiny and so can be neglected. I decided to chose 8 different lengths between 30-100cm because when I did a preliminary experiment I found that these lengths gave accurate results and that 8 readings was sufficient enough for me to plot a st. line graph and draw a good line of best fit through the points. Micrometer screw-gauge: – I decided to measure the diameter of the wire at 3 different positions on the wire. I then calculated the average diameter from the 3 measurements taken to enable me to measure the diameter of the wire as accurately as possible.