Which of the following statements about resistance is INCORRECT?

The correct answer is Resistance is constant for a given metallic wire at any temperature.

Key Points

• Resistance of a metallic wire depends on its temperature. As the temperature increases, the resistance of a metallic conductor also increases due to increased collisions of electrons.
• The statement "Resistance is constant for a given metallic wire at any temperature" is incorrect because resistance varies with temperature.
• For a given metallic wire, resistance remains constant only at a specific temperature, not at all temperatures.
• Ohm's law, which relates voltage, current, and resistance, assumes constant resistance only under stable temperature conditions.
• Materials like semiconductors and insulators exhibit a more complex relationship between resistance and temperature compared to metallic wires.

Additional Information

• Resistance (R):
  • It is a measure of the opposition to the flow of electric current in a conductor.
  • The SI unit of resistance is the ohm (Ω).
  • Resistance depends on material properties, length, cross-sectional area, and temperature of the conductor.
• Temperature Coefficient of Resistance:
  • It indicates how the resistance of a material changes with temperature.
  • Metals typically have a positive temperature coefficient, meaning their resistance increases with rising temperature.
• Rheostat:
  • A rheostat is a variable resistor used to control current by adjusting the resistance in a circuit.
  • It is commonly used for applications like dimming lights or controlling motor speed.
• Ohm’s Law:
  • It states that the current (I) through a conductor is directly proportional to the voltage (V) across it, provided the temperature remains constant.
  • The formula is: V = IR, where R is the resistance.
• Superconductors:
  • These are materials that exhibit zero resistance below a critical temperature.
  • Superconductors are used in technologies like MRI machines and particle accelerators.