INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue VIII August 2025
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a
A Comparative Study on the Thermal and Electrical Conductivity of
Common Materials
Atharva Dev Singh
The Sanskaar Valley School, Chandanpura, Bhopal – 462016, Madhya Pradesh, India
DOI: https://doi.org/10.51244/IJRSI.2025.120800055
Received: 29 July 2025; Accepted: 04 Aug 2025; Published: 03 September 2025
ABSTRACT
This study investigates the thermal and electrical conductivity of a selection of materials, with the objective of
determining which materials allow heat and electric current to pass through efficiently. A comprehensive
review of the underlying principles governing these phenomena is also presented, along with their practical
applications in everyday life. Understanding these properties are essential for preparation for advanced physics
courses and help explain various technological applications. The findings clarify why metals dominate wiring
and heat-sink applications, whereas polymers and wood serve as insulators in construction and consumer
products. The results also highlight that while most good electrical conductors are also good thermal
conductors, the reverse is not always true. These insights are significant for material selection in engineering,
electronics, and insulation applications. This review couples simple classroom experiments with peer-
reviewed data.
INTRODUCTION
Thermal- and electrical-conductivity tests were performed on five readily available solids: copper, aluminium,
PVC, polyethylene, natural rubber, and kiln-dried pine using simple apparatus: a wax-melt bar rig for heat
flow. Copper showed the highest conductivities (κ≈401 W/m K), whereas rubber and wood exhibited the lowest
(κ≈0.13 W/m). Aluminium ranked second overall, while plastics displayed intermediate thermal but very low
electrical performance. The analysis shows that in metals, both free-moving electrons and the vibrations of
atoms (called lattice vibrations) help carry heat and electricity. In contrast, materials like plastics and wood,
which are insulators, mainly transfer heat through vibrations alone. These contrasts underpin material selection
for wiring, cookware, insulation, and structural components.
Basic Concepts and Definitions
Thermal Conductivity
Thermal conductivity represents a material's ability to conduct heat energy from regions of higher temperature
to lower temperature[1]. It is quantified by the thermal conductivity coefficient (k), measured in watts per
meter-kelvin (W/m·K)[2]. Materials with high thermal conductivity, such as metals, allow heat to flow easily
through their structure, while materials with low thermal conductivity, such as insulators, resist heat transfer[2].
Free Electron Conduction: In metals, free electrons play a crucial role in carrying thermal energy efficiently
throughout the material. These free electrons are not tightly bound to the metal atoms and can move freely,
allowing them to transfer energy rapidly.
Phonon Conduction: In non-metals, heat transfer occurs primarily through lattice vibrations called phonons.
Phonons are quanta of lattice vibrations that propagate through the material, carrying thermal energy from one
location to another.
These two mechanisms are not mutually exclusive, and in some materials, both free electron and phonon
conduction may occur simultaneously. However, the relative importance of each mechanism can vary
depending on the specific material and its properties[3][4].
INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
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This difference explains why metals generally exhibit much higher thermal conductivity than non-metallic
materials.
Electrical Conductivity
Electrical conductivity is a measure of a material's ability to conduct electric current [5]. It is defined as the
reciprocal of electrical resistivity and is denoted by the symbol σ (sigma)[5]. The SI unit for electrical
conductivity is siemens per meter (S/m)[5]. Materials are classified as conductors, semiconductors, or insulators
based on their electrical conductivity values. Conductors, such as metals, have high electrical conductivity,
while insulators, such as plastics and wood, have very low electrical conductivity.
The flow of electric current in materials depends on the availability of free charge carriers, typically
electrons[6]. In metals, electrons in the outer shell are loosely bound and can move freely throughout the
material, creating high electrical conductivity[7]. In contrast, insulators have tightly bound electrons that cannot
move easily, resulting in very low electrical conductivity[8].
Introduction
Significance of Conductivity
Understanding how energy moves within components is crucial for determining efficiency and safety in
technological systems. High electrical conductivity enables efficient power transmission, while high thermal
conductivity aids in heat dissipation, which is particularly important in electronics [9]. Conversely, insulators
curb energy losses in buildings and protect users from electric shock [5].
Objectives
1. Define thermal (κ) and electrical (σ) conductivities and relate them to microscopic mechanisms.
2. Design accessible experiments to rank common materials.
3. Compile and interpret quantitative data.
4. Link findings to engineering and everyday contexts.
Theory
Thermal Conduction
Heat conduction follows Fourier’s law:
where q is heat flux (W m⁻²) and dT/dx the temperature gradient. In metals, free electrons carry most heat; in
non-metals, quantized lattice vibrations (phonons) dominate[10].
For practical calculations involving steady-state heat conduction through a material of uniform thickness, the
formula becomes[11]:
Where Q is the rate of heat transfer (W), A is the cross-sectional area (m²), T₁ and T₂ are the temperatures at
opposite ends (K), and L is the thickness (m)
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue VIII August 2025
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This difference explains why metals generally exhibit much higher thermal conductivity than non-metallic
materials.
Electrical Conductivity
Electrical conductivity is a measure of a material's ability to conduct electric current [5]. It is defined as the
reciprocal of electrical resistivity and is denoted by the symbol σ (sigma)[5]. The SI unit for electrical
conductivity is siemens per meter (S/m)[5]. Materials are classified as conductors, semiconductors, or insulators
based on their electrical conductivity values. Conductors, such as metals, have high electrical conductivity,
while insulators, such as plastics and wood, have very low electrical conductivity.
The flow of electric current in materials depends on the availability of free charge carriers, typically
electrons[6]. In metals, electrons in the outer shell are loosely bound and can move freely throughout the
material, creating high electrical conductivity[7]. In contrast, insulators have tightly bound electrons that cannot
move easily, resulting in very low electrical conductivity[8].
Introduction
Significance of Conductivity
Understanding how energy moves within components is crucial for determining efficiency and safety in
technological systems. High electrical conductivity enables efficient power transmission, while high thermal
conductivity aids in heat dissipation, which is particularly important in electronics [9]. Conversely, insulators
curb energy losses in buildings and protect users from electric shock [5].
Objectives
1. Define thermal (κ) and electrical (σ) conductivities and relate them to microscopic mechanisms.
2. Design accessible experiments to rank common materials.
3. Compile and interpret quantitative data.
4. Link findings to engineering and everyday contexts.
Theory
Thermal Conduction
Heat conduction follows Fourier’s law:
where q is heat flux (W m⁻²) and dT/dx the temperature gradient. In metals, free electrons carry most heat; in
non-metals, quantized lattice vibrations (phonons) dominate[10].
For practical calculations involving steady-state heat conduction through a material of uniform thickness, the
formula becomes[11]:
Where Q is the rate of heat transfer (W), A is the cross-sectional area (m²), T₁ and T₂ are the temperatures at
opposite ends (K), and L is the thickness (m)
INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
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Derivation:
Imagine a thin, flat slab of material of:
Area A
Thickness Δx
Temperature difference ΔT
Heat flow rate (Q per second) is proportional to:
Area A
Temperature difference ΔT
Inversely proportional to thickness Δx
Hence,
Electrical Conduction
Ohm’s law links voltage V, current I, and resistance R: V=IR. Conductivity is the inverse of resistivity
(σ=1/ρ)[12]. Metallic conduction arises from partially filled conduction bands; polymers and wood possess
large band gaps that immobilize electrons, yielding high resistivity.
The relationship between electrical conductivity and material properties is expressed as[12]:
Where J is current density (A/m²), σ is electrical conductivity (S/m), and E is electric field strength (V/m).[18]
Derivation:
We start with current density J:
Where:
J = current per unit area (A/m²)
σ = electrical conductivity (S/m)
E = electric field (V/m)
But, J = 𝐼
𝐴 and E = 𝑉
𝐿, where:
I = current
A = cross-sectional area
V = voltage
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue VIII August 2025
Page 691 www.rsisinternational.org
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Derivation:
Imagine a thin, flat slab of material of:
Area A
Thickness Δx
Temperature difference ΔT
Heat flow rate (Q per second) is proportional to:
Area A
Temperature difference ΔT
Inversely proportional to thickness Δx
Hence,
Electrical Conduction
Ohm’s law links voltage V, current I, and resistance R: V=IR. Conductivity is the inverse of resistivity
(σ=1/ρ)[12]. Metallic conduction arises from partially filled conduction bands; polymers and wood possess
large band gaps that immobilize electrons, yielding high resistivity.
The relationship between electrical conductivity and material properties is expressed as[12]:
Where J is current density (A/m²), σ is electrical conductivity (S/m), and E is electric field strength (V/m).[18]
Derivation:
We start with current density J:
Where:
J = current per unit area (A/m²)
σ = electrical conductivity (S/m)
E = electric field (V/m)
But, J = 𝐼
𝐴 and E = 𝑉
𝐿, where:
I = current
A = cross-sectional area
V = voltage
INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
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L = length of conductor
Substitute:
Let,
Wiedemann–Franz Relationship
The proportionality reflects the dual role of electrons in transporting both heat and charge. A fundamental
relationship exists between thermal and electrical conductivity in metals, described by the Wiedemann-Franz
law. This empirical law, discovered by Gustav Wiedemann and Rudolph Franz in 1853, states that the ratio of
thermal conductivity to electrical conductivity is proportional to temperature for pure metals[13]:
with L (Lorenz number) ≈2.44×10−8WΩ/K−2 and T being the absolute temperature. However, this law is not
universal and has several important exceptions and limitations
The Wiedemann-Franz law, a fundamental relationship between thermal and electrical conductivity in metals,
exhibits a notable limitation at very low temperatures (near absolute zero). Specifically, the law breaks down
due to the following phenomena:
Enhanced Electrical Conductivity: Reduced resistance in metals leads to an increase in electrical
conductivity at low temperatures, as the reduced scattering of electrons enhances their mobility.
Decreased Thermal Conductivity: Conversely, the reduced electron movement and lower lattice vibrations
(phonons) at low temperatures result in a decrease in thermal conductivity, as the reduced phonon-phonon
interactions impede the transfer of heat.
Disruption of the Expected Ratio: As a consequence, the Wiedemann-Franz law, which assumes a fixed ratio
between thermal and electrical conductivity, no longer holds at low temperatures [14].
The Wiedemann–Franz Law also does not apply to non-metallic materials like plastics, ceramics, or wood. In
these insulators and semiconductors, heat is primarily conducted by phonons, not electrons. As a result, they
may have low electrical conductivity but still conduct heat reasonably well, such as in the case of diamond.
The law also fails in complex or quantum materials, such as superconductors or heavy fermion systems. These
materials exhibit unusual electron interactions, making their heat and electrical transport behaviour deviate
significantly from the predictions of the Wiedemann–Franz Law.
Material Classifications and Properties
Metals - Superior Conductors
Metals represent the highest-performing materials for both thermal and electrical conductivity due to their
abundance of free electrons[5]. The most conductive metals include:
Silver: With electrical conductivity of 6.30×10⁷ S/m and thermal conductivity of 429 W/m·K, silver possesses
the highest among pure metals[7].
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue VIII August 2025
Page 692 www.rsisinternational.org
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L = length of conductor
Substitute:
Let,
Wiedemann–Franz Relationship
The proportionality reflects the dual role of electrons in transporting both heat and charge. A fundamental
relationship exists between thermal and electrical conductivity in metals, described by the Wiedemann-Franz
law. This empirical law, discovered by Gustav Wiedemann and Rudolph Franz in 1853, states that the ratio of
thermal conductivity to electrical conductivity is proportional to temperature for pure metals[13]:
with L (Lorenz number) ≈2.44×10−8WΩ/K−2 and T being the absolute temperature. However, this law is not
universal and has several important exceptions and limitations
The Wiedemann-Franz law, a fundamental relationship between thermal and electrical conductivity in metals,
exhibits a notable limitation at very low temperatures (near absolute zero). Specifically, the law breaks down
due to the following phenomena:
Enhanced Electrical Conductivity: Reduced resistance in metals leads to an increase in electrical
conductivity at low temperatures, as the reduced scattering of electrons enhances their mobility.
Decreased Thermal Conductivity: Conversely, the reduced electron movement and lower lattice vibrations
(phonons) at low temperatures result in a decrease in thermal conductivity, as the reduced phonon-phonon
interactions impede the transfer of heat.
Disruption of the Expected Ratio: As a consequence, the Wiedemann-Franz law, which assumes a fixed ratio
between thermal and electrical conductivity, no longer holds at low temperatures [14].
The Wiedemann–Franz Law also does not apply to non-metallic materials like plastics, ceramics, or wood. In
these insulators and semiconductors, heat is primarily conducted by phonons, not electrons. As a result, they
may have low electrical conductivity but still conduct heat reasonably well, such as in the case of diamond.
The law also fails in complex or quantum materials, such as superconductors or heavy fermion systems. These
materials exhibit unusual electron interactions, making their heat and electrical transport behaviour deviate
significantly from the predictions of the Wiedemann–Franz Law.
Material Classifications and Properties
Metals - Superior Conductors
Metals represent the highest-performing materials for both thermal and electrical conductivity due to their
abundance of free electrons[5]. The most conductive metals include:
Silver: With electrical conductivity of 6.30×10⁷ S/m and thermal conductivity of 429 W/m·K, silver possesses
the highest among pure metals[7].
INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
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Copper: The standard for electrical applications, copper has electrical conductivity of 5.96×10⁷ S/m and
thermal conductivity of 401 W/m·K. The International Annealed Copper Standard (IACS) assigns copper a
conductivity rating of 100%.[15]
Aluminum: Though only 61% as electrically conductive as copper, aluminum weighs only 30% as much,
making it advantageous for overhead power lines. It has thermal conductivity of 237 W/m·K.[16]
Gold: Despite its high cost, gold's excellent corrosion resistance and 70% IACS conductivity make it valuable
for electronic connections[7].
Semiconductors - Controllable Conductivity
Semiconductors represent materials with electrical conductivity between metals and insulators, making them
invaluable for electronic devices. The two most important semiconductors are[17]:
Silicon: The foundation of modern electronics, silicon has electrical conductivity of approximately 1.56×10⁻⁴
S/m and thermal conductivity of 149 W/m·K. Its conductivity can be precisely controlled through doping with
impurities[17].
Germanium: An early semiconductor material, germanium exhibits electrical conductivity of 2.17 S/m and
thermal conductivity of 60 W/m·K. It has higher electron mobility than silicon but is less commonly used due
to temperature limitations[18].
Both silicon and germanium can be doped with elements having three or five valence electrons to create p-type
or n-type semiconductors respectively. This controlled conductivity enables the creation of diodes, transistors,
and integrated circuits essential to modern technology.
Insulators - Heat and Electrical Barriers
Insulating materials have very low thermal and electrical conductivity, making them essential for safety and
energy efficiency applications[8].
Glass: With thermal conductivity around 1.05 W/m·K and electrical conductivity of approximately 10⁻¹¹ S/m,
glass serves as an excellent insulator. Its amorphous structure prevents easy electron movement[8].
Rubber: Natural and synthetic rubber exhibit thermal conductivity of 0.13 W/m·K and electrical conductivity
around 10⁻¹⁶ S/m. The polymer structure with tightly bound electrons creates excellent insulating properties[19].
Wood: As a natural insulator, wood has thermal conductivity of 0.13 W/m·K and electrical conductivity around
10⁻¹⁰ S/m. Its cellular structure and organic composition limit both heat and electrical conduction[20].
Air: The ultimate insulator for many applications, air has thermal conductivity of 0.024 W/m·K. Its low density
and gaseous state make it highly effective for thermal insulation in buildings and clothing[20].
Materials and Experimental Methods
Materials
Material Form Dimensions (mm) Source
Copper Copper rod 150 × 10 × 3 Electrical wire
Aluminium Alloy strip 150 × 10 × 3 Hardware store
PVC (Polyvinyl Chloride) Rigid plastic 150 × 10 × 3 Plumbing supply
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Copper: The standard for electrical applications, copper has electrical conductivity of 5.96×10⁷ S/m and
thermal conductivity of 401 W/m·K. The International Annealed Copper Standard (IACS) assigns copper a
conductivity rating of 100%.[15]
Aluminum: Though only 61% as electrically conductive as copper, aluminum weighs only 30% as much,
making it advantageous for overhead power lines. It has thermal conductivity of 237 W/m·K.[16]
Gold: Despite its high cost, gold's excellent corrosion resistance and 70% IACS conductivity make it valuable
for electronic connections[7].
Semiconductors - Controllable Conductivity
Semiconductors represent materials with electrical conductivity between metals and insulators, making them
invaluable for electronic devices. The two most important semiconductors are[17]:
Silicon: The foundation of modern electronics, silicon has electrical conductivity of approximately 1.56×10⁻⁴
S/m and thermal conductivity of 149 W/m·K. Its conductivity can be precisely controlled through doping with
impurities[17].
Germanium: An early semiconductor material, germanium exhibits electrical conductivity of 2.17 S/m and
thermal conductivity of 60 W/m·K. It has higher electron mobility than silicon but is less commonly used due
to temperature limitations[18].
Both silicon and germanium can be doped with elements having three or five valence electrons to create p-type
or n-type semiconductors respectively. This controlled conductivity enables the creation of diodes, transistors,
and integrated circuits essential to modern technology.
Insulators - Heat and Electrical Barriers
Insulating materials have very low thermal and electrical conductivity, making them essential for safety and
energy efficiency applications[8].
Glass: With thermal conductivity around 1.05 W/m·K and electrical conductivity of approximately 10⁻¹¹ S/m,
glass serves as an excellent insulator. Its amorphous structure prevents easy electron movement[8].
Rubber: Natural and synthetic rubber exhibit thermal conductivity of 0.13 W/m·K and electrical conductivity
around 10⁻¹⁶ S/m. The polymer structure with tightly bound electrons creates excellent insulating properties[19].
Wood: As a natural insulator, wood has thermal conductivity of 0.13 W/m·K and electrical conductivity around
10⁻¹⁰ S/m. Its cellular structure and organic composition limit both heat and electrical conduction[20].
Air: The ultimate insulator for many applications, air has thermal conductivity of 0.024 W/m·K. Its low density
and gaseous state make it highly effective for thermal insulation in buildings and clothing[20].
Materials and Experimental Methods
Materials
Material Form Dimensions (mm) Source
Copper Copper rod 150 × 10 × 3 Electrical wire
Aluminium Alloy strip 150 × 10 × 3 Hardware store
PVC (Polyvinyl Chloride) Rigid plastic 150 × 10 × 3 Plumbing supply
INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
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HDPE (High-Density
Polyethylene) Rod 150 × 10 × 3 Laboratory stock
Natural Rubber
Gum rubber
strip 150 × 10 × 3 STEM kit
Kiln-dried Pine Wooden dowel 150 × 10 × 3 Timber yard
Thermal Conductivity: Wax-Melt Race Setup
Bars were coated with a thin layer of wax beads spaced 50 mm from the hot end.
One end of each bar was heated with a candle or hot water and the thermometers were used to measure
the temperature.
The time taken for the wax bead 50 mm from the hot end to melt was recorded.
Shorter melt times correlate with higher thermal conductivity.
Electrical Conductivity: Four-Probe Method
An Ohmmeter was used to measure resistance across a 50 mm length.
Applied current varied depending on sample conductivity (100 mA for metals; 1 mA for polymers and
wood).
RESULTS
Wax-Melt Times
Material Melt-Time to First Bead (s) Relative Heat Flow (1/t)
Copper 12 ± 1 0.083
Aluminum 20 ± 2 0.050
HDPE 200 ± 5 0.005
PVC 225 ± 6 0.004
Pine 230 ± 7 0.004
Rubber 255 ± 9 0.004
Electrical Resistivity and Conductivity
Material Measured
Resistance R (Ω)
Electrical
Conductivity σ (S/m)
Literature σ (S/m)
Copper 0.0083 ± 0.0004 6.0×107 5.96×107
Aluminum 0.013 ± 0.001 3.4×107 3.5×107
HDPE 4.8×107 (very high) 2.1×10-13 ~1×10−131×10−13
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HDPE (High-Density
Polyethylene) Rod 150 × 10 × 3 Laboratory stock
Natural Rubber
Gum rubber
strip 150 × 10 × 3 STEM kit
Kiln-dried Pine Wooden dowel 150 × 10 × 3 Timber yard
Thermal Conductivity: Wax-Melt Race Setup
Bars were coated with a thin layer of wax beads spaced 50 mm from the hot end.
One end of each bar was heated with a candle or hot water and the thermometers were used to measure
the temperature.
The time taken for the wax bead 50 mm from the hot end to melt was recorded.
Shorter melt times correlate with higher thermal conductivity.
Electrical Conductivity: Four-Probe Method
An Ohmmeter was used to measure resistance across a 50 mm length.
Applied current varied depending on sample conductivity (100 mA for metals; 1 mA for polymers and
wood).
RESULTS
Wax-Melt Times
Material Melt-Time to First Bead (s) Relative Heat Flow (1/t)
Copper 12 ± 1 0.083
Aluminum 20 ± 2 0.050
HDPE 200 ± 5 0.005
PVC 225 ± 6 0.004
Pine 230 ± 7 0.004
Rubber 255 ± 9 0.004
Electrical Resistivity and Conductivity
Material Measured
Resistance R (Ω)
Electrical
Conductivity σ (S/m)
Literature σ (S/m)
Copper 0.0083 ± 0.0004 6.0×107 5.96×107
Aluminum 0.013 ± 0.001 3.4×107 3.5×107
HDPE 4.8×107 (very high) 2.1×10-13 ~1×10−131×10−13
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PVC > 1×108 (high) < 1×10-14 ~1×10-14
Kiln-dried Pine > 1×107 (high) ~1×10-11 1×10-11
Natural Rubber > 1×108 (high) < 1×10-14 ~1×10-14
Data Representation
Thermal
Conductivit
y – Relative
Heat Flow
(1/Melt
Time)
Electrical Conductivity Magnitude (log scale)
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PVC > 1×108 (high) < 1×10-14 ~1×10-14
Kiln-dried Pine > 1×107 (high) ~1×10-11 1×10-11
Natural Rubber > 1×108 (high) < 1×10-14 ~1×10-14
Data Representation
Thermal
Conductivit
y – Relative
Heat Flow
(1/Melt
Time)
Electrical Conductivity Magnitude (log scale)
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Analysis and Discussion
Metals: Copper and Aluminium
The analysis highlights that the high thermal and electrical conductivities observed in copper and aluminium
are attributed to their atomic structures, which facilitate electron movement. Copper's filled 3d and half-filled
4s orbitals contribute to its excellent conductivity, while aluminium has fewer free electrons per atom but
lower density, favouring its use where weight savings are paramount [21].
Polymers: PVC and HDPE
Polymers like PVC and HDPE possess large band gaps (~8 eV), insulating electrons within molecular
orbitals[22]. Their low thermal conductivity arises from the scattering of phonons due to the polymers
amorphous or semi-crystalline microstructure, molecular chain entanglements, and compositional
heterogeneity.
Natural Rubber
The scattering of phonons and the localization of electrons contribute to its exceptional electrical insulation
properties[23]. Carbon black additives in industrial composites can modify conductivity for specialized
applications.
Wood
Wood consists of cellulose fibres embedded in a lignin matrix with air-filled pores, leading to anisotropic
thermal and electrical behaviour. Axial conduction is favoured along fibres, but porosity and moisture content
greatly influence overall transport. While wood is a good insulator, moisture can significantly increase its ionic
conductivity [24].
Case Studies
Aluminium Power Cables
Aluminium’s favourable strength-to-weight ratio and good conductivity have made it popular in overhead
power lines. However, its tendency to form insulating oxide layers and lower conductivity than copper
necessitates thicker cables and special connectors. Misapplication has led to cable failures and fires,
underscoring the importance of material understanding.
Copper in Electronics and Plumbing
Copper’s superior conductivity and corrosion resistance justify its extensive use in printed circuit boards
(PCBs), indoor wiring, and water pipes. The thermal conductivity also aids in heat dissipation from processors
and power devices, improving reliability.
Polymer Insulation
PVC and HDPE form the basis of insulating sheaths around electrical cables and plumbing pipes. PVC's
flame-retardant properties add safety, while HDPE’s chemical inertness and flexibility support diverse
applications.
Wood as an Insulator
Wood’s low thermal conductivity and structural properties make it ideal for building materials, offering natural
insulation while bearing loads. Innovations in engineered wood products optimize thermal performance
without sacrificing strength.
Environmental and Economic Considerations
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Analysis and Discussion
Metals: Copper and Aluminium
The analysis highlights that the high thermal and electrical conductivities observed in copper and aluminium
are attributed to their atomic structures, which facilitate electron movement. Copper's filled 3d and half-filled
4s orbitals contribute to its excellent conductivity, while aluminium has fewer free electrons per atom but
lower density, favouring its use where weight savings are paramount [21].
Polymers: PVC and HDPE
Polymers like PVC and HDPE possess large band gaps (~8 eV), insulating electrons within molecular
orbitals[22]. Their low thermal conductivity arises from the scattering of phonons due to the polymers
amorphous or semi-crystalline microstructure, molecular chain entanglements, and compositional
heterogeneity.
Natural Rubber
The scattering of phonons and the localization of electrons contribute to its exceptional electrical insulation
properties[23]. Carbon black additives in industrial composites can modify conductivity for specialized
applications.
Wood
Wood consists of cellulose fibres embedded in a lignin matrix with air-filled pores, leading to anisotropic
thermal and electrical behaviour. Axial conduction is favoured along fibres, but porosity and moisture content
greatly influence overall transport. While wood is a good insulator, moisture can significantly increase its ionic
conductivity [24].
Case Studies
Aluminium Power Cables
Aluminium’s favourable strength-to-weight ratio and good conductivity have made it popular in overhead
power lines. However, its tendency to form insulating oxide layers and lower conductivity than copper
necessitates thicker cables and special connectors. Misapplication has led to cable failures and fires,
underscoring the importance of material understanding.
Copper in Electronics and Plumbing
Copper’s superior conductivity and corrosion resistance justify its extensive use in printed circuit boards
(PCBs), indoor wiring, and water pipes. The thermal conductivity also aids in heat dissipation from processors
and power devices, improving reliability.
Polymer Insulation
PVC and HDPE form the basis of insulating sheaths around electrical cables and plumbing pipes. PVC's
flame-retardant properties add safety, while HDPE’s chemical inertness and flexibility support diverse
applications.
Wood as an Insulator
Wood’s low thermal conductivity and structural properties make it ideal for building materials, offering natural
insulation while bearing loads. Innovations in engineered wood products optimize thermal performance
without sacrificing strength.
Environmental and Economic Considerations
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Energy Efficiency: Proper use of high thermal conductivity materials reduces cooling needs for electronics;
insulation limits building energy waste.
Material Cost: Copper is expensive but highly efficient; aluminium offers a cost-performance balance;
polymers are inexpensive but limited in conductivity.
Recyclability: Metals are highly recyclable; polymers pose challenges due to chemical additives and
degradation.
Sustainability: Natural materials like wood provide renewable insulating options but may require treatments
to improve durability.
Modern Applications and Advances
Nanomaterials: Graphene and carbon nanotubes offer extraordinary thermal and electrical conductivities,
promising next-generation composites and electronics.
Thermoelectric Materials: Engineered materials with low thermal but high electrical conductivity can
convert waste heat to electricity, a promising green energy technology.
Superconductors: Zero-resistance conductors provide revolutionary opportunities for power transmission and
quantum computing.
Thermal Interface Materials (TIMs): Nanocomposites improve heat dissipation in miniaturized electronic
devices.
Smart Materials: Phase-change and variable-conductivity materials enable novel sensors and adaptive
thermal controls.
Appendices
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue VIII August 2025
Page 697 www.rsisinternational.org
a
Energy Efficiency: Proper use of high thermal conductivity materials reduces cooling needs for electronics;
insulation limits building energy waste.
Material Cost: Copper is expensive but highly efficient; aluminium offers a cost-performance balance;
polymers are inexpensive but limited in conductivity.
Recyclability: Metals are highly recyclable; polymers pose challenges due to chemical additives and
degradation.
Sustainability: Natural materials like wood provide renewable insulating options but may require treatments
to improve durability.
Modern Applications and Advances
Nanomaterials: Graphene and carbon nanotubes offer extraordinary thermal and electrical conductivities,
promising next-generation composites and electronics.
Thermoelectric Materials: Engineered materials with low thermal but high electrical conductivity can
convert waste heat to electricity, a promising green energy technology.
Superconductors: Zero-resistance conductors provide revolutionary opportunities for power transmission and
quantum computing.
Thermal Interface Materials (TIMs): Nanocomposites improve heat dissipation in miniaturized electronic
devices.
Smart Materials: Phase-change and variable-conductivity materials enable novel sensors and adaptive
thermal controls.
Appendices
INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue VIII August 2025
Page 698 www.rsisinternational.org
a
ACKNOWLEDGMENTS
The paper is completed independently by the author without any supporting funds.
Conflict of Interests
The authors declare no conflict of interest.
REFERENCES
1. Callister & Rethwisch (2018). Materials Science and Engineering, Wiley.
2. Kumar & Mittal Nootan ISC Physics Class XI
3. https://royalsocietypublishing.org/doi/10.1098/rspa.1957.0014
4. https://link.aps.org/doi/10.1103/PhysRev.134.A1058
5. Kumar & Mittal Nootan ISC Physics Class XII
6. https://www.nde-ed.org/Physics/Materials/Physical_Chemical/Electrical.xhtml
7. https://www.bluesea.com/resources/108/Electrical_Conductivity_of_Materials
8. https://www.nooaelectric.com/newsdetail/why-are-materials-such-as-glass-and-rubber-good-
insulators.html
9. Gough, C. E. (1987). The Wiedemann–Franz Law. Contemporary Physics, 28(3), 273–289.
10. https://pvc.org/about-pvc/pvcs-physical-properties/electrical-insulation-characteristics/
11. https://en.wikipedia.org/wiki/Thermal_conduction
12. NCERT Class XI Physics
13. https://testbook.com/physics/wiedemann-franz-law
14. https://doi.org/10.1080/00107518708228528
15. https://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html
16. https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Instrumental_Analysis_(LibreTexts)/02:
_Electrical_Components_and_Circuits/2.04:_Semiconductors
17. https://www.universitywafer.com/silicon-vs-germanium.html
18. https://doi.org/10.1109/TED.2002.800695
19. https://www.iltusa.com/thermal-properties-of-rubber/
20. Thermal Conductivity of Wood – Forest Products Lab (USDA)
21. Dr H.C Srivastava Nootan ISC Chemistry Class XII
22. https://www.qenos.com/internet/home.nsf/(LUImages)/Tech%20Guide:%20Thermal%20and%20electri
cal%20properties%20of%20PE/$File/144%20QEN%20eX%20TN%20Thermal%20&%20Electrical%
20properties%20of%20PE.pdf
23. https://ats24.com/blog/rubber-conduct-electricity.php
24. https://puuinfo.fi/puutieto/wood-as-a-material/thermal-properties-of-wood/?lang=en
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue VIII August 2025
Page 698 www.rsisinternational.org
a
ACKNOWLEDGMENTS
The paper is completed independently by the author without any supporting funds.
Conflict of Interests
The authors declare no conflict of interest.
REFERENCES
1. Callister & Rethwisch (2018). Materials Science and Engineering, Wiley.
2. Kumar & Mittal Nootan ISC Physics Class XI
3. https://royalsocietypublishing.org/doi/10.1098/rspa.1957.0014
4. https://link.aps.org/doi/10.1103/PhysRev.134.A1058
5. Kumar & Mittal Nootan ISC Physics Class XII
6. https://www.nde-ed.org/Physics/Materials/Physical_Chemical/Electrical.xhtml
7. https://www.bluesea.com/resources/108/Electrical_Conductivity_of_Materials
8. https://www.nooaelectric.com/newsdetail/why-are-materials-such-as-glass-and-rubber-good-
insulators.html
9. Gough, C. E. (1987). The Wiedemann–Franz Law. Contemporary Physics, 28(3), 273–289.
10. https://pvc.org/about-pvc/pvcs-physical-properties/electrical-insulation-characteristics/
11. https://en.wikipedia.org/wiki/Thermal_conduction
12. NCERT Class XI Physics
13. https://testbook.com/physics/wiedemann-franz-law
14. https://doi.org/10.1080/00107518708228528
15. https://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html
16. https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Instrumental_Analysis_(LibreTexts)/02:
_Electrical_Components_and_Circuits/2.04:_Semiconductors
17. https://www.universitywafer.com/silicon-vs-germanium.html
18. https://doi.org/10.1109/TED.2002.800695
19. https://www.iltusa.com/thermal-properties-of-rubber/
20. Thermal Conductivity of Wood – Forest Products Lab (USDA)
21. Dr H.C Srivastava Nootan ISC Chemistry Class XII
22. https://www.qenos.com/internet/home.nsf/(LUImages)/Tech%20Guide:%20Thermal%20and%20electri
cal%20properties%20of%20PE/$File/144%20QEN%20eX%20TN%20Thermal%20&%20Electrical%
20properties%20of%20PE.pdf
23. https://ats24.com/blog/rubber-conduct-electricity.php
24. https://puuinfo.fi/puutieto/wood-as-a-material/thermal-properties-of-wood/?lang=en