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Questions and Answers
Which of the following factors does not affect the resistance of a wire?
Which of the following factors does not affect the resistance of a wire?
- Temperature of the wire
- Color of the wire's insulation (correct)
- Shape of the wire's cross-section
- Material the wire is made of
What is the unit of resistivity?
What is the unit of resistivity?
- Ohms per square meter
- Meter-ohms
- Ohms per meter (correct)
- Ohm-meters
How does the cross-sectional area of a wire affect its resistance?
How does the cross-sectional area of a wire affect its resistance?
- The cross-sectional area affects the resistance only in copper wires
- Decreasing the cross-sectional area increases the resistance
- The cross-sectional area does not affect the resistance
- Increasing the cross-sectional area decreases the resistance (correct)
What is the purpose of measuring the diameter of a wire multiple times?
What is the purpose of measuring the diameter of a wire multiple times?
What is the relationship between the resistance of a wire and its length?
What is the relationship between the resistance of a wire and its length?
What is the formula for the resistivity of a material?
What is the formula for the resistivity of a material?
What is the primary reason why longer wires have higher resistance?
What is the primary reason why longer wires have higher resistance?
A wire with a circular cross-section has a diameter of 2mm. What is its cross-sectional area?
A wire with a circular cross-section has a diameter of 2mm. What is its cross-sectional area?
In an experiment to measure the resistivity of a material, what is the purpose of plotting a graph of resistance against length?
In an experiment to measure the resistivity of a material, what is the purpose of plotting a graph of resistance against length?
What is the advantage of using a material with low resistivity for making wires?
What is the advantage of using a material with low resistivity for making wires?
If the resistance of a wire is measured to be 5 ohms, and the cross-sectional area is 0.01m², what is the resistivity of the material?
If the resistance of a wire is measured to be 5 ohms, and the cross-sectional area is 0.01m², what is the resistivity of the material?
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Study Notes
Factors Affecting Resistance
- Resistance of a wire depends on its length, with longer wires having higher resistance due to increased difficulty for electrons to flow.
- Thicker wires (larger cross-sectional area) have lower resistance, similar to how water flows more easily through a wide pipe.
- The material the wire is made of also affects resistance, with copper being a good electrical conductor.
- Resistance (R) is equal to the resistivity of the material (ρ) multiplied by the length (L) and divided by the cross-sectional area (A).
Resistivity
- Resistivity (ρ) is a property of the material and is equal to RA/L.
- For a wire with a circular cross-section, the area (A) is equal to πr² (or πd²/4).
Experimental Measurement of Resistivity
- To find the resistivity of a material, measure the resistance of a wire and how it changes with length.
- Measure voltage divided by current to find the resistance, and plot a graph of resistance against length to get a straight line.
- The gradient of the line is equal to ρ divided by A, so the resistivity can be found.
- Take multiple measurements of the diameter to ensure an accurate and reliable value.
Factors Affecting Resistance
- Longer wires have higher resistance due to increased difficulty for electrons to flow.
- Thicker wires (larger cross-sectional area) have lower resistance.
- The material's conductivity affects resistance, with copper being a good electrical conductor.
- Resistance (R) = resistivity (ρ) × length (L) ÷ cross-sectional area (A).
Resistivity
- Resistivity (ρ) is a property of the material, equal to RA/L.
- For a wire with a circular cross-section, area (A) = πr² (or πd²/4).
Experimental Measurement of Resistivity
- Measure resistance by finding voltage ÷ current.
- Plot a graph of resistance against length to get a straight line.
- The gradient of the line is equal to ρ ÷ A, allowing resistivity to be found.
- Take multiple measurements of the diameter for an accurate and reliable value.
Factors Affecting Resistance
- Longer wires have higher resistance due to increased difficulty for electrons to flow.
- Thicker wires (larger cross-sectional area) have lower resistance.
- The material's conductivity affects resistance, with copper being a good electrical conductor.
- Resistance (R) = resistivity (ρ) × length (L) ÷ cross-sectional area (A).
Resistivity
- Resistivity (ρ) is a property of the material, equal to RA/L.
- For a wire with a circular cross-section, area (A) = πr² (or πd²/4).
Experimental Measurement of Resistivity
- Measure resistance by finding voltage ÷ current.
- Plot a graph of resistance against length to get a straight line.
- The gradient of the line is equal to ρ ÷ A, allowing resistivity to be found.
- Take multiple measurements of the diameter for an accurate and reliable value.
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