Correct statement regarding resistance

(a) Resistance opposes current flow
(b) Independent of temperature
(c) Independent of material
(d) None

Correct Answer: (a) Resistance opposes current flow

Explanation

Resistance is the property of a conductor that opposes the flow of current.

Notes for More Information

Resistance

1. Resistance is the property of a conductor that opposes the flow of electric current through it.
2. It is denoted by R.
3. The SI unit of resistance is the ohm (Ω).
4. In a metallic wire:
• Resistance is directly proportional to its length.
• Resistance is inversely proportional to its cross-sectional area.

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Formula for Resistance

5. The resistance of a conductor is given by:

6. Where:
•  = resistance (Ω)
•  = resistivity of the material
•  = length of the conductor
•  = cross-sectional area of the conductor

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Effect of Temperature on Resistance

7. For pure metals, resistance increases when temperature increases.
8. This behavior is called the positive temperature coefficient of resistance.
9. For semiconductors and insulators, resistance decreases when temperature increases.
10. This behavior is called the negative temperature coefficient of resistance.

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Temperature Coefficient of Resistance

11. Let the resistance of a metallic conductor at 0°C be .
12. When the temperature is increased to t°C, the resistance becomes .
13. Increase in resistance:

14. The increase in resistance depends on:
• The initial resistance
• The rise in temperature
• The nature of the material
15. Therefore:

16. Or,

17. Here, α is a constant known as the temperature coefficient of resistance.
18. From the above relation:

19. The resistance at temperature t°C is:

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Conclusion

20. Resistance increases with the length of the conductor.
21. Resistance decreases with an increase in cross-sectional area.
22. Resistance depends on the resistivity, which depends on the nature of the material.
23. Resistance also depends on the temperature of the conductor.
24. Resistance is an inherent property of a material that opposes the flow of current.
25. When current flows, electrons collide with atoms, which slows their movement and causes resistance.
26. Higher resistance results in less current flow for a given voltage.