Measurement of Resistivity of Highly Resistive Material
1. What is an alloy?
An alloy is a combination of two or more elements, where at least one element is a metal.
Alloys are designed to improve specific properties such as strength, corrosion resistance, or
electrical conductivity. Examples include steel (iron + carbon), brass (copper + zinc), and
bronze (copper + tin).
2. What is resistance and resistivity? Hence differentiate them.
• Resistance (R): The opposition offered by a material to the flow of electric current.
It depends on the material, its length, area of cross-section, and temperature.
Formula: R=ρLAR = \rho \frac{L}{A}
• Resistivity (ρ): A material-specific property that quantifies how strongly a material
opposes the flow of electric current. It depends only on the nature and
temperature of the material.
Formula: ρ=RAL\rho = R \frac{A}{L}
Parameter Resistance Resistivity
Definition Opposition to current Material-specific opposition
Symbol RR ρ\rho
Unit Ohm (Ω) Ohm-meter (Ω·m)
Dependence Length, area, material, temp. Only material and temperature
3. What is the unit of resistance and resistivity?
• Resistance (R): The unit is Ohm (Ω).
• Resistivity (ρ): The unit is Ohm-meter (Ω·m).
4. Why only DC supply is applied for resistance measurement?
DC supply is applied because AC introduces reactive components such as inductance and
capacitance, which can affect accurate resistance measurement. DC avoids these
complications and provides a steady current for precise measurement.
5. Name different types of alloys used in electrical engineering.
• Nichrome (Nickel + Chromium): Used in heating elements.
• Eureka (Copper + Nickel): Used in precision resistors.
• Kanthal (Iron + Chromium + Aluminum): Used for high-temperature applications.
• Brass (Copper + Zinc): Used in connectors and terminals.
• Solder (Tin + Lead): Used in joining electrical components.
6. What is Standard Wire Gauge (SWG) and its use?
SWG is a standard system for measuring the diameter of wires. It is used to determine the
cross-sectional area of conductors for calculating electrical resistance and current-carrying
capacity.
, 7. List the factors on which resistance and resistivity depend.
• Resistance:
o Length of the material (LL)
o Cross-sectional area (AA)
o Resistivity of the material (ρ\rho)
o Temperature
• Resistivity:
o Nature of the material
o Temperature
8. What is the outcome of the experiment?
The outcome of the experiment is the measured value of resistivity of a highly resistive
material using the formula:
ρ=RAL\rho = R \frac{A}{L}
where RR is the measured resistance, AA is the cross-sectional area, and LL is the length of
the material.
9. Give some examples of alloys with their composition.
Alloy Composition
Nichrome 80% Nickel, 20% Chromium
Brass 60-70% Copper, 30-40% Zinc
Bronze 90% Copper, 10% Tin
Kanthal Iron, Chromium, Aluminum
Eureka 55% Copper, 45% Nickel
10. What are the different applications of Nichrome, Eureka, Kanthal?
• Nichrome: Used in heating elements of toasters, ovens, and electric heaters.
• Eureka: Used in precision resistors and thermocouples.
• Kanthal: Used in high-temperature furnaces, heating coils, and industrial heating
applications.
11. Draw circuit diagram of the experiment along with specifications of apparatus used in
it.
Apparatus: Ammeter, voltmeter, power supply (DC), test specimen (resistive material),
rheostat, and connecting wires.
Circuit Diagram:
• Voltage is applied across the specimen, and current is measured using an ammeter.
Voltage drop is recorded using a voltmeter.
1. What is an alloy?
An alloy is a combination of two or more elements, where at least one element is a metal.
Alloys are designed to improve specific properties such as strength, corrosion resistance, or
electrical conductivity. Examples include steel (iron + carbon), brass (copper + zinc), and
bronze (copper + tin).
2. What is resistance and resistivity? Hence differentiate them.
• Resistance (R): The opposition offered by a material to the flow of electric current.
It depends on the material, its length, area of cross-section, and temperature.
Formula: R=ρLAR = \rho \frac{L}{A}
• Resistivity (ρ): A material-specific property that quantifies how strongly a material
opposes the flow of electric current. It depends only on the nature and
temperature of the material.
Formula: ρ=RAL\rho = R \frac{A}{L}
Parameter Resistance Resistivity
Definition Opposition to current Material-specific opposition
Symbol RR ρ\rho
Unit Ohm (Ω) Ohm-meter (Ω·m)
Dependence Length, area, material, temp. Only material and temperature
3. What is the unit of resistance and resistivity?
• Resistance (R): The unit is Ohm (Ω).
• Resistivity (ρ): The unit is Ohm-meter (Ω·m).
4. Why only DC supply is applied for resistance measurement?
DC supply is applied because AC introduces reactive components such as inductance and
capacitance, which can affect accurate resistance measurement. DC avoids these
complications and provides a steady current for precise measurement.
5. Name different types of alloys used in electrical engineering.
• Nichrome (Nickel + Chromium): Used in heating elements.
• Eureka (Copper + Nickel): Used in precision resistors.
• Kanthal (Iron + Chromium + Aluminum): Used for high-temperature applications.
• Brass (Copper + Zinc): Used in connectors and terminals.
• Solder (Tin + Lead): Used in joining electrical components.
6. What is Standard Wire Gauge (SWG) and its use?
SWG is a standard system for measuring the diameter of wires. It is used to determine the
cross-sectional area of conductors for calculating electrical resistance and current-carrying
capacity.
, 7. List the factors on which resistance and resistivity depend.
• Resistance:
o Length of the material (LL)
o Cross-sectional area (AA)
o Resistivity of the material (ρ\rho)
o Temperature
• Resistivity:
o Nature of the material
o Temperature
8. What is the outcome of the experiment?
The outcome of the experiment is the measured value of resistivity of a highly resistive
material using the formula:
ρ=RAL\rho = R \frac{A}{L}
where RR is the measured resistance, AA is the cross-sectional area, and LL is the length of
the material.
9. Give some examples of alloys with their composition.
Alloy Composition
Nichrome 80% Nickel, 20% Chromium
Brass 60-70% Copper, 30-40% Zinc
Bronze 90% Copper, 10% Tin
Kanthal Iron, Chromium, Aluminum
Eureka 55% Copper, 45% Nickel
10. What are the different applications of Nichrome, Eureka, Kanthal?
• Nichrome: Used in heating elements of toasters, ovens, and electric heaters.
• Eureka: Used in precision resistors and thermocouples.
• Kanthal: Used in high-temperature furnaces, heating coils, and industrial heating
applications.
11. Draw circuit diagram of the experiment along with specifications of apparatus used in
it.
Apparatus: Ammeter, voltmeter, power supply (DC), test specimen (resistive material),
rheostat, and connecting wires.
Circuit Diagram:
• Voltage is applied across the specimen, and current is measured using an ammeter.
Voltage drop is recorded using a voltmeter.
