Metals generally conduct electricity. This is because their atoms have a pool of mobile valence electrons (electrons present in the outermost shell of an atom).
The freedom of these electrons allows them to travel through the lattices present in metals and respond positively to any electric field.
In other words, metals with more rapid movements undergo numerous collisions and will conduct electricity better than those with slight movement.
I will dig deeper into why metals conduct electricity, their varying conductivity, and the factors that affect them. In addition, you will also learn about the various real-life applications of conducting metals.
How Do Metals Conduct Electricity?
There are several characteristics responsible for the natural conduction of metals. The two major ones are:
1. Metallic bonding
The metallic bonding in metals allows their atoms to readily share their valence electrons. This results in the availability of a pool of delocalized electrons ready to conduct when a voltage or electric source is introduced.
Metallic bonding is also responsible for metals’ malleability, high melting point, ductility, strength, and thermal conductivity.
2. Band gap
Another factor responsible for the easy conduction of electricity in metals is their band gap. The band gap is the distance between valence bands and conduction bands.
Metals have no gap between their valence and conduction bands because they overlap. Hence, electrons can move from one atom to another once they have enough energy.
Electrical Conductivity of Metals
The electrical conductivity of a metal is the measure of the amount of electricity it can carry or allow to pass through it. Since most metals are good conductors, they exhibit high conductivity.
The electrical conductivity of any metal can be measured using:
σ = l/RA
Where:
- σ = Electrical conductivity
- R = Resistance of the material
- A = Cross-sectional area of material
- L = Length of material
Here is a breakdown of popular metals and their conductivity (in descending order):
| Metals | Conductivity σ x 106 (S/m) |
| Silver | 63.00 |
| Copper (Cu) | 59.60 |
| Gold (Au) | 41.10 |
| Aluminum (Al) | 37.70 |
| Calcium (Ca) | 29.80 |
| Niobium (Nb) | 7.00 |
| Lead (Pb). | 4.55 |
| Titanium (Ti) | 2.38 |
| Mercury (Hg) | 1.02 |
| Manganese (Mn) | 0.69 |
Electrical Resistivity of Metals
The opposite of electrical conductivity is resistivity (or resistance). In other words, it measures how much a metal is willing to oppose the flow of electricity.
The electrical resistivity of any metal can be measured using:
ρ = RA/l
Where:
- ρ = Resistivity
- R = Resistance of the material
- A = Cross-sectional area of material
- L = Length of material
Here is a table displaying the resistivity of popular metals:
| Metals | Resistivity ρ x 10-3 (Ω.m) |
| Mercury (Hg) | 8.90 |
| Iron (Fe) | 6.41 |
| Nickel (Ni) | 6.41 |
| Tungsten (W) | 4.50 |
| Copper (Co) | 4.29 |
| Tin (Sn) | 4.20 |
| Platinum (Pt) | 3.93 |
| Aluminum (Al) | 3.80 |
| Silver (Ag) | 1.59 |
Do Metals Conduct Heat?
Most metals are good conductors of heat. This is thanks to the presence of freely moving delocalized electrons. When metals gain heat, these electrons move more rapidly and bump into one another.
These collisions result in the conduction of heat energy from the hot end to the colder region of a metal until the heat circulates. In other words, it is safe to say most metals have decent to high thermal resistivity.
The thermal conductivity of any metal can be measured using:
K = (QL)/(AΔT)
Where:
- K = Thermal conductivity
- Q = The amount of heat transferred through the metal
- L = The distance between the two isothermal planes
- A = The area of the surface
- ΔT = The difference in temperature
Here is a table containing the thermal resistivity of common metals:
| Metals | Thermal Conductivity at Room Temperature (W/m•K) |
| Copper | 397 |
| Aluminum | 226 |
| Tungsten | 197 |
| Magnesium | 151 |
| Brass | 117 |
| Zinc | 112 |
| Nickel | 88 |
| Iron | 72 |
| Bronze(Aluminum) | 71 |
| Carbon Steel | 71 |
| Steel carbon type 1020 (0.2 – 0.6 c) | 71 |
| Tin | 62 |
| Stainless Steel (446) | 23 |
| Titanium | 21 |
Factors Affecting How Metals Conduct Electricity
There are several factors capable of altering the conductivity of metals. Let’s see the significant ones:
1. Temperature
An increase in temperature reduces the conductivity of metals. This is because photon-electron interactions exert a linear decrease in conductivity.
When lattice vibrations cease, and electrons pass through metal atoms unimpeded, metals like copper and silver become superconductors.
2. Shape
The size and shape of a metal play a greater role in its extrinsic (external) resistance than in its intrinsic resistivity.
Since resistance is the amount of electron flow per cross-sectional area, it is safe to say a wire’s (usually made of metals) resistance will be higher if it is longer and thinner and vice versa.
This is why engineers prefer thicker wires for high-voltage operations.
3. Impurity atoms
Just as an increase in temperature reduces conductivity, numerous impurities do the same. This is because impurity atoms reduce electron mobility, especially in metal alloys.
Most alloys become susceptible to reduced conductivity when their base metal is replaced, and its lattice gets stressed. If this substitution does not stress the base metal, precipitates will.
This is why one of the easiest ways to measure the conductivity of a metal is to check for precipitates.
4. Grain boundaries
Engineers and other manufacturers also control the conductivity of metals by modifying grain boundaries. Grain boundaries are where two crystal structures with different orientations meet.
When these boundaries undergo lattice strain, election mobility reduces resulting in lesser conductivity. Hence, it is safe to say abundant grain boundaries are essential for better conduction and vice versa.
Uses of Metal
- Copper features in electrical wiring more than other metals because it is widely available, anti-corrosive, and budget-friendly.
- Some applications also make use of aluminum wires because they are lighter.
- Gold or silver plays a role in coating contacts, mirrors, and conductors in telecom devices.
- Mercury (a liquid metal) is an essential part of some thermometers.
- Bridge and house constructions usually require metals like iron and steel.
- Zinc is often used in protecting iron from rushing. This is a process known as galvanization.
FAQs
Do alloys conduct electricity in a molten state?
Yes, metal alloys conduct electricity in their molten state by losing electrons to form cations.
These electrons efficiently carry out the conduction.
What metal isn’t conductive?
Bismuth is a metal that poorly conducts electricity.
Its resistivity is so high that it can be considered a dielectric material.
Which metal conducts electricity but not heat?
Vanadium dioxide is a metal that conducts electricity but cannot conduct heat.
Ideally, it is an insulator, but at 67°C, it transforms into a metal with this unique property.
Conclusion
Metals generally conduct electricity and heat very well because their electrons move freely in the presence of an electric potential. Since charges repel one another, this conduction flows only in one direction (toward the positive end).
When two or more metals get combined (as seen in alloys), electrical and thermal conductivity reduces. This is because atoms of different weights and sizes will vibrate and move at different rates.
Also, there are metals that are practically insulators.
I hope you found this guide helpful. Thanks for reading.
