Resistivity is a fundamental property of materials that quantifies how strongly they resist the flow of electric current. It is defined as the resistance of a material per unit length and cross-sectional area, typically measured in ohm-meters (Ω·m). The resistivity of a material is influenced by temperature; as temperature increases, the resistivity of most conductors, such as metals, also increases. This is due to the increased thermal agitation of atoms in the lattice structure, which leads to more frequent collisions between free electrons and lattice atoms, thereby impeding the flow of electrons. Conversely, some materials, like semiconductors, exhibit a decrease in resistivity with increasing temperature, as more charge carriers become available for conduction. Understanding the relationship between resistivity and temperature is crucial for designing and optimizing electrical components and circuits.
What is the difference between resistance and resistivity?
Resistance: It is the opposition to the flow of electric current in a particular wire. Its
unit is Ω(ohm).
Resistivity: It is a material property that defines the resistance of a unit cube of the
material. Its unit is Ωm.
How does resistivity depend on temperature?
Resistivity of most conductors increases with temperature because the vibration of atoms increases, causing more frequent collisions with electrons. For semiconductors, resistivity decreases with an increase in temperature.
Why are copper and silver commonly used in electrical wires?
Copper and silver have very low resistivity, making them excellent conductors of electricity. Additionally, they have good mechanical properties and stability over a range of temperatures.
What happens to the resistance of a conductor and a semiconductor when temperature increases?
For conductors: Resistance increases with temperature due to more frequent electron collisions.
For semiconductors: Resistance decreases with temperature because more charge carriers are generated.
Why does the resistivity of insulators remain almost constant with temperature changes?
The resistivity of insulators is already very high, and temperature changes do not significantly affect the availability of charge carriers. As a result, their resistivity remains nearly constant over a wide temperature range.
What does the resistivity of a material depend on?
a) Length of the wire
b) Cross-sectional area of the wire
c) Material of the wire
d) Voltage applied
Answer: c) Material of the wire
Which of the following is the SI unit of resistivity?
a) Ohm
b) Ohm-meter
c) Siemens
d) Ohm per meter
Answer: b) Ohm-meter
What happens to the resistivity of a conductor as the temperature increases?
a) Decreases
b) Increases
c) Remains constant
d) Becomes zero
Answer: b) Increases
Which material is the best conductor of electricity based on resistivity?
a) Aluminum
b) Copper
c) Silver
d) Iron
Answer: c) Silver
Which type of material shows a decrease in resistance with an increase in temperature?
a) Metals
b) Insulators
c) Semiconductors
d) Alloys
Answer: c) Semiconductors