Comparison Table: Resistance and Resistivity Explained with Examples
The topic Difference Between Resistance And Resistivity is important for physics exams, as it helps students differentiate physical properties of materials versus components. Proper understanding aids in solving questions on electric circuits and material properties in JEE, NEET, and board exams.
Definition of Resistance
Resistance is a property of a material or object that opposes the flow of electric current. It quantifies how strongly a conductor hinders the movement of electric charge. The standard unit of resistance is the ohm (Ω).
The resistance of a conductor depends on its length, area of cross-section, and material type. For more conceptual clarity, refer to Understanding Electrical Resistance.
Definition of Resistivity
Resistivity, also called specific resistance, is an intrinsic property of a material that describes how strongly it resists current flow. It is independent of the shape or size of the sample and is denoted by the symbol ρ (rho).
The resistivity of a material allows comparison of different materials’ ability to conduct electricity. The SI unit of resistivity is ohm-meter (Ω·m). For similar concepts, see Ohmic vs Non-Ohmic Conductors.
Difference Table
| Resistance | Resistivity |
|---|---|
| Property of a specific object or conductor | Property of the material itself |
| Depends on length, area, and material | Depends only on nature and temperature of material |
| Symbol is R | Symbol is ρ (rho) |
| Measured in ohms (Ω) | Measured in ohm-meters (Ω·m) |
| R = ρ(l/A) is the formula | ρ = R·A/l is the formula |
| Varies with length and area of the object | Constant for a given material at a fixed temperature |
| Changes with physical dimensions of conductor | Unaffected by physical dimensions |
| Can be increased by increasing length | Cannot be changed by changing length or area |
| Used to characterize circuit elements | Used to characterize materials |
| Resistance changes with temperature (for conductors) | Resistivity also changes with temperature but is characteristic to each material |
| Expressed as a function of geometry and material | Expressed only for the material property |
| Has dimensional formula ML2T-3A-2 | Has dimensional formula ML3T-3A-2 |
| Can be measured directly in circuits | Usually measured indirectly through resistance |
| Different for different shapes of same material | Remains same for all shapes of given material |
| Calculated for a given wire or device | Standard value listed for material |
| Written as R in circuit diagrams | Written as ρ in material property tables |
| Can be decreased by increasing cross-sectional area | Does not depend on cross-sectional area |
| Important for circuit analysis | Important for material selection |
| Resistance is affected if material is replaced | Resistivity remains constant unless material is changed |
| Related to other properties like impedance | Inverse of conductivity; fundamental material property |
Key Differences
- Resistance refers to an object, resistivity to material
- Resistance depends on dimensions; resistivity does not
- Resistance is measured in ohms; resistivity in ohm-meter
- Resistance changes with geometry; resistivity stays constant
- Resistivity helps compare material properties for conduction
Examples
A copper wire with length 2 m and area 1 mm2 has a resistance calculated using R = ρ(l/A), where ρ for copper is 1.68 × 10-8 Ω·m. Changing wire length changes resistance, not resistivity.
If two wires are of same material and length but different cross-sectional areas, their resistances differ, but their resistivity remains same. Explore related concepts at Resistance vs Impedance.
Applications
- Resistance used to design electrical circuits and components
- Resistivity used in selecting materials for wires or resistors
- Resistance important in load calculations for safety devices
- Resistivity guides development of conductors and insulators
- Circuit analysis applies resistance for current and voltage control
- Material engineering uses resistivity to identify suitable materials
One-Line Summary
In simple words, resistance measures how an object resists current, whereas resistivity quantifies how a material opposes current flow inherently.
FAQs on What Is the Difference Between Resistance and Resistivity?
1. What is the difference between resistance and resistivity?
Resistance is the property of a material that opposes the flow of electric current, while resistivity is the intrinsic property of a material that determines how strongly it resists current flow.
Key differences:
- Resistance depends on length, area, and temperature of the conductor.
- Resistivity only depends on the type/material and temperature.
- Resistance is measured in ohms (Ω), resistivity in ohm-meter (Ω·m).
- Formula: R = ρ (L/A) where R = resistance, ρ = resistivity, L = length, A = area.
2. Define resistance and resistivity in physics.
Resistance is the opposition offered by a conductor to the flow of electric current. Resistivity is the material’s unique property that quantifies how strongly it resists current flow.
Factors:
- Resistance (R) depends on length, cross-sectional area, and temperature.
- Resistivity (ρ) is constant for a specific material at a certain temperature.
3. How is resistance related to resistivity?
Resistance (R) of a conductor is directly proportional to its resistivity (ρ), and length (L), and inversely proportional to cross-sectional area (A).
Mathematically:
- R = ρ (L/A)
- Where R = resistance, ρ = resistivity, L = length, A = area.
4. What are the units of resistance and resistivity?
The SI unit of resistance is ohm (Ω), while the SI unit of resistivity is ohm-meter (Ω·m).
- Resistance (R): Measures how much material resists the flow of current.
- Resistivity (ρ): Quantifies material's inherent opposition irrespective of dimensions.
5. Why is resistivity considered a property of the material?
Resistivity is unique for each material and does not change with size or shape, only with temperature.
- It helps differentiate conductors, semiconductors, and insulators.
- Depends solely on the molecular structure and type of material.
6. What factors affect the resistance of a wire?
The resistance of a wire depends on several factors:
- Length of wire (directly proportional)
- Cross-sectional area (inversely proportional)
- Material (resistivity)
- Temperature (generally increases resistance)
7. How can you calculate the resistance of a conductor?
The resistance (R) of a conductor is calculated using the formula:
- R = ρ (L/A)
- Where ρ is resistivity, L is length, and A is cross-sectional area.
8. What is the significance of resistivity in classifying materials?
Resistivity is essential for classifying materials as conductors, semiconductors, or insulators.
- Low resistivity: Good conductors (e.g., metals)
- Moderate resistivity: Semiconductors (e.g., silicon)
- High resistivity: Insulators (e.g., rubber, glass)
9. Give two examples each of conductors and insulators based on resistivity.
Based on resistivity, examples are:
- Conductors: Copper (Cu), Aluminium (Al)
- Insulators: Glass, Rubber
10. What are the applications of resistance and resistivity in real life?
Both resistance and resistivity play crucial roles in electrical and electronic applications.
Some uses include:
- Designing electrical wiring and circuits
- Selecting suitable materials for heating elements
- Manufacturing resistors and insulators
- Electrical safety and device efficiency
11. Can two wires of different materials have the same resistance?
Yes, two wires made from different materials can have the same resistance if the ratio of their resistivity, length, and area compensate each other.
Key points:
- Resistance depends on resistivity, length, and area.
- Adjusting these factors makes identical resistance possible.
12. How does temperature affect resistance and resistivity?
Temperature generally increases both resistance and resistivity in conductors.
- For metals: Both rise with temperature.
- For semiconductors: Resistivity decreases with increase in temperature.
- This concept is vital for understanding devices like thermistors.
13. Explain with formula how resistance and resistivity are measured.
- Resistance (R): Measured as V/I (Ohm’s law), where V is voltage, I is current.
- Resistivity (ρ): Calculated using ρ = R × (A/L), where R is resistance, A is area, L is length.
