Electricty has embedded itself so pervasively in the background of our day-to-day experience that we grow accustomed to it and yet forget that at base it is about something incredibly small: electric charge. The sudden shock you experience by running a finger down a metallic doorknob or the great power grids that illuminate a whole city are a one-to-one product of the charming characteristics and actions of the electric charge.
Herein, in this article, we shall embark upon an exhaustive study of such properties in considerable detail—looking at what a charge is, how a charge acts under different conditions, and why charge occupies such a prominent spot as one of the core foundation stones upon which rests contemporary science and technology as we know it today.
Types of Electric Charge
1. Positive and Negative Charges
The most basic fact about electric charge is that it comes in two kinds: positive and negative. You can think of them as complete opposites. When two objects have opposite charges—one positive and the other negative—they pull toward each other. But if both objects have the same type of charge, like two positives or two negatives, they push away from each other. This easy rule, “opposites attract, likes repel,” explains many things, such as why a balloon sticks to a wall after rubbing it on your hair.
Positive charges are associated with protons, found inside the atomic nucleus. Negative charges are carried by electrons, which orbit around the nucleus.
2. Neutrality in Nature
Most objects we see around us appear electrically neutral. This doesn’t mean they lack charge altogether. Instead, it means they have equal amounts of positive and negative charges, which cancel out.
For example, a simple plastic pen contains trillions of positive charges in its protons and the exact same number of negative charges in its electrons. Since they balance each other perfectly, the pen shows no net charge. Only when electrons are transferred (like when you rub it against your shirt) does the pen become charged.
Additivity of Charges
1. Charges Add Like Numbers
Another important property is that charges are additive. If you place several charged bodies together in a system, the net charge is just the algebraic sum of all individual charges.
This means electric charge is a scalar quantity—it doesn’t have direction, only magnitude and sign (positive or negative).
For instance:
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If you have a body with +3 C of charge and another with -1 C, the total charge of the system is +2 C.
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If both have -2 C, the total is -4 C.
It’s as straightforward as simple addition.
2. Importance of Sign Convention
The sign (+ or -) is not just a label; it matters a lot. Mixing up the signs can completely change the outcome of a calculation. For example, in physics problems, adding +5 C and -5 C gives a net charge of zero, not ten.
This also means two objects with equal and opposite charges can neutralize each other if brought together—a fact widely used in electronics and daily life.
Conservation of Charge
1. Charge Cannot Be Created or Destroyed
Perhaps the most fundamental law about charge is the conservation of charge. In an isolated system, the total charge remains constant.
No matter how charges move around, get transferred, or redistributed, the net total doesn’t change. This principle is as universal as the law of conservation of energy.
2. Everyday Example of Conservation
Take the common example of rubbing a plastic rod with a piece of cloth. When you do this, electrons move from the cloth to the rod. The rod becomes negatively charged, while the cloth becomes positively charged.
But here’s the key: the amount of negative charge gained by the rod is exactly equal to the positive charge gained by the cloth. Nothing extra is created or lost.
This is why scientists say “charge is conserved.”
Quantisation of Charge
1. Smallest Unit of Charge
Unlike mass, which seems to vary smoothly, electric charge comes in discrete packets. The smallest indivisible unit of charge is carried by the electron (negative) or proton (positive).
This fundamental charge has a value of:
e = 1.6 × 10⁻¹⁹ coulomb
This means that every observable charge in the universe is an integer multiple of this number. You can have 2e, 5e, or 1000e—but you will never encounter 0.5e or 1.3e.
2. Visible Only at Microscopic Level
At the atomic and subatomic levels, this quantisation is very obvious. For instance, a hydrogen nucleus always has exactly +1e charge.
But in daily life, charges appear so large that this discreteness becomes invisible. Imagine a single coulomb of charge—it equals about 6.25 × 10¹⁸ electrons. With numbers that big, the quantisation looks more like a smooth flow.
Measuring Electric Charge
1. Coulomb as the Standard Unit
In the SI system, the unit of charge is the coulomb (C).
One coulomb is defined as the amount of charge transferred when a current of one ampere flows for one second.
This might sound small, but in reality, one coulomb is a huge amount of charge. That’s why scientists often work with smaller practical units.
2. Smaller Practical Units
Instead of using full coulombs, charges are often measured in:
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Millicoulombs (mC) = 10⁻³ C
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Microcoulombs (μC) = 10⁻⁶ C
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Nanocoulombs (nC) = 10⁻⁹ C
For example, the static charge on a rubbed balloon may be just a few microcoulombs, but that’s still enough to make your hair stand on end.
Real-World Examples of Electric Charge
1. Electrons in a Copper Cube
Visualize a small cube of copper, just 1 cm³ in volume. Each atom in the copper contains one free electron, and packed in this small volume are about 8.5 × 10²² atoms. The total therefore is about 2.5 × 10²⁴ free electrons.
If you were to work out the amount of charge in these electrons, you'd find it is stupendous—billions of coulombs. It's boggling one's mind to think about how huge quantities of charge sit quietly in everyday matter.
2. Charges in a Cup of Water
Even water holds an astronomical amount of hidden charge. A single cup of water contains roughly 10²⁴ molecules. Each molecule has equal positive and negative charges, balancing each other.
If you somehow separated them (which you can’t in practice), you’d end up with around 10⁷ coulombs of positive charge on one side and the same amount of negative charge on the other.
This example shows why neutrality in nature is so important. If all that charge were unbalanced, life as we know it wouldn’t exist.
Why These Properties Matter
Understanding the properties of electric charge isn’t just academic. These principles are the foundation of everything from household appliances to satellite communication.
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The types of charge explain how circuits and components interact.
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Additivity allows us to calculate total charge and predict outcomes.
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Conservation of charge ensures the consistency of electrical laws and is essential in designing safe power systems.
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Quantisation is the backbone of modern quantum physics and electronics.
Every gadget you use, every light you switch on, every computer you work with—it all functions because these properties are always, without fail, true.
Conclusion
Electric charge is invisible, but it affects almost everything around us. It is very small, yet it controls many things in our daily life. There are two types of charge: positive and negative. Opposite charges attract each other. Same charges push away from each other. Charges can add up. They are never lost or created. They also come in tiny fixed amounts, called quantisation. Scientists can measure charge with special tools.
Charges are everywhere. Electrons in atoms have negative charge. Protons in the nucleus have positive charge. Lightning is a huge flow of charge in the sky. The electricity in our homes also follows these rules. Knowing about charge has helped humans make lights, phones, computers, and many other things. Charges are small and invisible, but they shape the world we live in.