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An experiment was set up to find the resistivity of the material of a wire - Leaving Cert Physics - Question 4 - 2018
Question 4
An experiment was set up to find the resistivity of the material of a wire. (i) Draw a labelled diagram of the apparatus used in this experiment. (ii) What measure... show full transcript
Worked Solution & Example Answer:An experiment was set up to find the resistivity of the material of a wire - Leaving Cert Physics - Question 4 - 2018
Step 1
Draw a labelled diagram of the apparatus used in this experiment.
Answer
To draw the labelled diagram, include the following components:
- Wire: Represent the wire whose resistivity is being measured.
- Ammeter: Connect in series to measure the current flowing through the wire.
- Voltmeter: Connect in parallel across the wire to measure the voltage.
- Power Supply: Indicate a battery or power source that provides the necessary voltage.
- Rheostat: Use to adjust the current in the circuit.
- Circuit connections: Use connecting wires to show how the components are linked.
Make sure to label each part clearly to convey the purpose of each component.
Step 2
What measurements were taken during this experiment?
Answer
In the experiment, the following measurements were taken:
- Length of the Wire: Measured using a ruler or measuring tape to determine the length of the wire used.
- Diameter/Cross-sectional Area: Measured using a micrometer or caliper to find the diameter of the wire, which can be used to calculate its cross-sectional area using the formula: , where is the radius of the wire.
- Current: Measured using an ammeter to find the current flowing through the wire.
- Voltage: Measured using a voltmeter to find the potential difference across the wire.
Step 3
How were these measurements used to calculate the resistivity?
Answer
The measurements obtained from the experiment were utilized to calculate the resistivity () of the material of the wire using the formula:
Where:
- is the resistance of the wire, calculated using Ohm’s law from the measurements of voltage (V) and current (I) as:
- is the cross-sectional area of the wire, calculated from the diameter.
- is the length of the wire.
By substituting the values of resistance, cross-sectional area, and length into the formula, the resistivity of the wire can be determined.
Step 4
State two precautions which the student might have taken to improve the accuracy of this experiment.
Answer
To improve the accuracy of the resistivity experiment, the student might take the following precautions:
- Minimize Temperature Variations: Ensure that the temperature of the environment remains constant, as resistance can vary with temperature.
- Calibration of Instruments: Regularly calibrate the ammeter and voltmeter to ensure accurate readings of current and voltage. This can be done by checking their output against known standards.