(a) dimensions
(b) material composition
(c) resistance
(d) both (a) and (b)
Correct Answer: (b) material
composition
Explanation
Resistivity is a material property, independent of
dimensions.
Notes for
More Information
CONCEPT: Specific Resistance
(Resistivity)
1. Specific
resistance, also called resistivity, is denoted by ρ.
2. Resistivity
is an intrinsic property of a material.
3. It depends
on:
·
Material composition
·
Temperature
4. It
does not depend on:
·
Length of the conductor
·
Cross-sectional area
·
Shape or size of the conductor
5. Hence, the
correct answer is:
Definition of Specific
Resistance
6. Specific
resistance (resistivity) is defined as:
The resistance offered by a material of unit
length and unit cross-sectional area at a given
temperature.
7. The SI unit
of resistivity is ohm-meter (Ω·m).
Formula
8. The
resistance of a conductor is given by:
Where:
= resistance (Ω)
= resistivity (Ω·m)
= length of conductor
= cross-sectional area
9. From this
relation:
Explanation
10.
Different materials have
different resistivities:
- Copper
→ low resistivity
- Aluminum
→ higher than copper
- Silicon
→ much higher resistivity
11.
As temperature changes, the resistivity of most materials
also changes.
12.
Dimensions (length and area) affect
the resistance of a particular wire, not the resistivity of
the material.
13.
Therefore, resistivity is often called intrinsic resistivity.
Important Clarification
14.
Resistance (R) depends on:
- Material
- Length
- Cross-sectional
area
- Temperature
15.
Resistivity (ρ) depends only on:
- Nature
of material
- Temperature
Final Conclusion (Exam Line)
16.
The specific resistance of a wire depends on the temperature and
the material used, and not on its dimensions.
17.
Hence, the correct answer is:
