Electric charge

Everything is made of tiny parts.

These parts have a special power. This power can be plus or minus.

Like powers push each other away. But different powers pull together. This is how things move.

Tiny bits called protons are plus. Tiny bits called electrons are minus. Most things have the same amount of both. This means they stay calm.

If the amounts are not the same, things change. This can make a spark. You might see it when you rub things.

This power is always there. It is a part of our world.

Everything in our world has a special property called electric charge.

Charge can be positive or negative. Like charges push each other away. This is called repulsion. Different charges pull toward each other. This is called attraction.

Most things are neutral. This means they have no net charge. Inside atoms, tiny parts carry the charge. Protons carry a positive charge. Electrons carry a negative charge. If an atom has equal numbers of both, it stays neutral. If it has more electrons, it becomes negative. If it has fewer, it becomes positive.

Charge comes in small units. We call the smallest unit the elementary charge.

An electron has one unit of negative charge. A proton has one unit of positive charge. Charges can move. When electrons move in one direction, we call it an electric current. You can even make static electricity. This happens when you rub two things together. One thing might take electrons from the other. This leaves one part positive and one part negative. Scientists measure charge using a unit called the coulomb.

Electric charge is a special property of matter. It causes things to feel a force when they are near an electromagnetic field.

This force can either pull things together or push them apart. There are two kinds of charge: positive and negative. If two objects have the same kind of charge, they will repel each other. If they have different charges, they will attract each other. Most things we touch are electrically neutral. This means they have no net charge at all.

To understand how this works, we must look inside atoms. Atoms are made of tiny parts called subatomic particles. Protons carry a positive charge, while electrons carry a negative charge. In most matter, the number of protons and electrons is equal. This balance makes the object neutral. If an object gains extra electrons, it becomes negative. If it loses electrons, it becomes positive. These charged atoms or groups of atoms are called ions.

People have studied these forces for a very long time. Ancient Greeks noticed that rubbing amber with fur could attract light objects. A man named Thales of Miletus lived around 600 BC and saw this effect. Later, in 1600, William Gilbert wrote about it in a book called De Magnete. He used the word "electrica," which is where we get the word "electricity." In the 1700s, Benjamin Franklin helped define charge. He used a glass rod rubbed with silk to show positive charge.

Charge is not a continuous flow like water. Instead, it is quantized, which means it comes in small, set units. The smallest unit that can exist freely is called the elementary charge, or "e." An electron has a charge of exactly −e. A proton has a charge of exactly +e. Scientists use the coulomb (C) as the main unit to measure charge. This unit was named after the French physicist Charles-Augustin de Coulomb. In 1897, J. J. Thomson discovered the electron, which helped us understand these units.

You can see electric charge in your own life. Static electricity happens when you rub two materials together. This can move electrons from one thing to another. You might feel a tiny spark or see your hair stand up. When electrons move in one direction through a metal, it is called an electric current. This movement of charge is what powers our world. Even the lightning in the sky is a massive display of electric charge moving through the air.

Electric charge is a fundamental physical property of matter. It causes matter to experience a force when placed within an electromagnetic field. This field is a combination of an electric field and a magnetic field. The interaction between charges and these fields creates the electromagnetic force, also known as the Lorentz force. This interaction is one of the four fundamental interactions in physics. Charge can be either positive or negative. Like charges repel one another, while unlike charges attract. Most objects we encounter are electrically neutral. This means they have no net charge because their internal components balance out.

To understand charge, we must look at subatomic particles. In ordinary matter, negative charge is carried by electrons. Positive charge is carried by protons located in the atomic nuclei. If an object has more electrons than protons, it carries a negative charge. If it has fewer electrons than protons, it is positive. When the numbers are equal, the object is neutral. Atoms can also become ions, which are charged atoms or groups of atoms. An atom that loses electrons becomes a cation with a positive charge. An atom that gains electrons becomes an anion with a negative charge. Monatomic ions consist of single atoms, while polyatomic ions involve bonded groups.

Electric charge is quantized, meaning it exists in discrete, specific amounts. It does not flow in a continuous stream like water. Instead, it comes in integer multiples of the elementary charge, represented by the symbol "e." This "e" is the smallest charge that can exist freely. A proton has a charge of +e, and an electron has a charge of −e. While particles called quarks have fractional charges, they are never found alone. They always combine to form particles with an integer multiple of the elementary charge. In the Standard Model of physics, charge is considered an absolutely conserved quantum number. This means the total charge in an isolated system never changes over time.

Humans have observed electrical phenomena since ancient times. The Greeks noticed that rubbing amber with fur attracted light objects. A mathematician named Thales of Miletus lived around 624 to 546 BC. He may have observed this, though he thought it showed that inanimate objects had souls. In 1600, William Gilbert published "De Magnete." He coined the term "electrica," which led to our modern word "electricity." Gilbert hypothesized that an "effluvium," or a stream of particles, caused this effect. Later, in 1729, Stephen Gray discovered that charge could be transmitted over a distance. He used twine to move charge 765 feet.

Scientists use specific units to measure these quantities. The SI derived unit for electric charge is the coulomb (C). This unit is named after the French physicist Charles-Augustin de Coulomb. One coulomb is the charge passing through a conductor carrying one ampere for one second. In physics and chemistry, scientists often use the elementary charge (e) as a unit. Chemists also use the Faraday constant. This constant represents the charge of one mole of elementary charges. In electrical engineering, the ampere-hour (A⋅h) is also a common measurement.

We see charge in action through several different phenomena. Static electricity occurs when an object has a non-zero, motionless net charge. This often happens by rubbing two different materials together, such as glass with silk. This process moves electrons from one material to another. When electrons move through conductive metals in a specific direction, it is called an electric current. Even when an object is neutral, it can become polarized. Polarization happens when charge is distributed non-uniformly within the object. This can be caused by an external electromagnetic field or by bound polar molecules.

Understanding electric charge connects many different scientific fields. It links the study of tiny subatomic particles to the massive forces of lightning. It also connects chemistry to physics through the study of ions and atomic structures. The study of how charged particles interact via photons is called quantum electrodynamics. This field helps us understand the most basic building blocks of our universe. By studying charge, we learn how matter interacts with the fundamental forces that shape everything around us.