With copper being one of the most widely used conducting metals, you may think pennies are good conductors of electricity. But what about the zinc and other metal alloys that are mixed into pennies? Do these change a penny’s conductive properties? Let’s take a dive into the details.

If you’re short on time, here’s a quick answer: Pennies are conductors due to their copper content, but newer pennies contain more zinc which lowers conductivity.

What Makes a Material a Good Conductor?

When it comes to determining whether a material is a good conductor or not, there are a few key factors to consider. Let’s take a closer look at what makes a material a good conductor.

High Mobility of Free Electrons

One of the main characteristics of a good conductor is the high mobility of free electrons within the material. In a conductor, the outermost electrons of the atoms are loosely bound and can move freely. This allows for the easy flow of electric current through the material.

Metals, such as copper and aluminum, are known for their high electron mobility and are widely used as conductors in various applications.

Metallic Bonding Structure

The metallic bonding structure is another key factor that contributes to a material’s conductivity. In metals, the atoms are arranged in a regular lattice structure, with the outermost electrons shared among all the atoms.

This creates a “sea” of delocalized electrons that are not bound to any particular atom. As a result, these electrons can move freely throughout the material, facilitating the flow of electric current.

A good way to understand the metallic bonding structure is to imagine a crowd of people holding hands in a circle. Each person represents an atom, and the hands represent the shared electrons. The electrons can freely move from one person to another, allowing for the easy transfer of energy.

It’s important to note that not all materials have high electron mobility or a metallic bonding structure. Insulators, for example, have tightly bound electrons that are not easily able to move. This restricts the flow of electric current and makes them poor conductors.

Examples of insulators include rubber, plastic, and wood.

For more information on the conductivity of materials, you can visit websites such as Explain That Stuff and Physics Classroom.

Pennies are Mostly Copper, Which Conducts Electricity Well

When it comes to determining if a penny is a conductor or insulator, it’s important to understand the composition of this small coin. Pennies, primarily used in the United States, are mostly made of copper.

Copper is well-known for its excellent electrical conductivity, making it a popular choice in electrical wiring and other applications where efficient electrical flow is desired.

Older Pennies are Nearly 100% Copper

In the past, pennies were predominantly made of copper. From 1793 to 1837, pennies were made of pure copper and were excellent conductors of electricity. Even in the years following, when the composition changed slightly, older pennies were still nearly 100% copper.

These older pennies would easily conduct electricity due to the high copper content.

Newer Pennies have More Zinc, But Still Conduct

As time went on, the composition of pennies changed. In 1982, the United States Mint began producing pennies with a zinc core and a thin copper plating. This change was made to reduce manufacturing costs, as zinc is a more affordable material than copper.

However, even with this change, pennies still have enough copper to maintain their electrical conductivity.

While newer pennies have a higher percentage of zinc, typically around 97.5%, the thin layer of copper on the outside still allows them to conduct electricity. This is because copper is a highly conductive metal, and even a small amount of it is sufficient to facilitate the flow of electrical current.

It’s worth noting that the electrical conductivity of pennies can vary slightly depending on their condition and age. Over time, the copper plating on newer pennies may wear off, exposing more of the zinc core. However, even in this state, pennies can still be considered conductors.

To summarize, pennies are mostly made of copper, a metal known for its excellent electrical conductivity. While newer pennies have a higher zinc content, the thin layer of copper on the outside allows them to conduct electricity.

So, the next time you find yourself wondering if a penny is a conductor or insulator, rest assured that it is indeed a conductor, thanks to its copper composition.

Other Factors That Impact a Penny’s Conductivity

Oxidation Can Reduce Conductivity Over Time

One of the key factors that can affect the conductivity of a penny is oxidation. Over time, pennies made of copper can develop a layer of oxide on their surface. This layer acts as an insulator, hindering the flow of electric current through the coin.

Oxidation occurs when copper reacts with oxygen in the air, forming copper oxide. This process is accelerated in moist or humid environments. As a result, older pennies may have a lower conductivity compared to newer ones that haven’t undergone significant oxidation.

It’s important to note that the effect of oxidation on a penny’s conductivity can vary depending on the thickness and uniformity of the oxide layer. A thin and uniform layer may not have a significant impact on conductivity, while a thicker and uneven layer can greatly reduce it.

Therefore, if you’re conducting electrical experiments using pennies, it’s advisable to use newer coins or clean the older ones to remove the oxide layer and ensure accurate results.

Pennies Have a Low Cross-Sectional Area

Another factor that affects a penny’s conductivity is its cross-sectional area. Pennies have a relatively small cross-sectional area compared to other objects commonly used as conductors, such as wires or metal rods.

The cross-sectional area of a conductor affects its ability to carry electric current. A larger area allows for more electrons to flow through the conductor, resulting in higher conductivity.

Due to their small size, pennies may not be as efficient at conducting electricity as larger objects with a larger cross-sectional area. This is why pennies are often used in simple electrical experiments or demonstrations, rather than for practical applications that require high conductivity.

However, it’s worth mentioning that the conductivity of a penny can still be influenced by other factors, such as its composition, cleanliness, and surface condition.

For more in-depth information on the conductivity of pennies and the science behind it, you can refer to Scientific American’s article on why pennies turn green over time.

Conductivity Experiments with Pennies

Measuring Resistance of Multiple Pennies

One interesting experiment to determine whether a penny is a conductor or an insulator is by measuring their resistance. Resistance is a measure of how well a material can resist the flow of electric current.

To conduct this experiment, you will need a multimeter, a power source, and multiple pennies.

Start by connecting the multimeter to the power source and setting it to measure resistance. Then, take two pennies and place them on a non-conductive surface, such as a piece of paper or a plastic tray.

Connect the positive and negative leads of the multimeter to the two pennies, making sure they are in direct contact with the metal surface.

Observe the resistance reading on the multimeter. If the reading is close to zero or very low, it indicates that the pennies are acting as conductors, allowing the flow of electric current. On the other hand, if the reading is high or infinite, it suggests that the pennies are acting as insulators, preventing the flow of electric current.

Repeat this experiment with multiple pennies and compare the resistance readings. This will help you determine if the conductivity of pennies is consistent or if it varies between different coins. Keep in mind that the results may vary due to factors such as age, wear, and composition of the pennies.

Using Pennies in Simple Circuits

Pennies can also be used in simple circuits to explore their conductivity further. A simple circuit consists of a power source, connecting wires, and a load, such as a light bulb or a buzzer.

To create a simple circuit using pennies, start by connecting a wire from the positive terminal of the power source to one penny. Then, connect another wire from the negative terminal of the power source to a second penny.

Finally, connect a wire from one penny to the load and another wire from the load to the other penny.

Switch on the power source and observe if the load, such as the light bulb, illuminates or if the buzzer sounds. If the load operates, it indicates that the pennies are acting as conductors, allowing the flow of electric current in the circuit.

If the load does not operate, it suggests that the pennies are acting as insulators, preventing the flow of electric current.

Remember to exercise caution when working with electricity and always follow safety guidelines. Experimenting with pennies in circuits can be a fun and educational way to learn about conductivity and the properties of different materials.


While pennies are considered conductors, their conductivity depends on composition and condition. Older copper-heavy pennies conduct better than newer pennies containing more zinc alloy. Oxidation also reduces conductivity over time.

But even newer pennies have enough copper to conduct electricity for simple experiments and circuits.

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