To understand electricity, some basic information about atoms is helpful. Atoms are the building blocks of the universe. Everything in the universe is made of atoms—every star, every tree, and every animal. The human body is made of atoms. Air and water are made of atoms, too. Atoms are so small that millions of them would fit on the head of a pin.
Atoms are made of even smaller particles
The center of an atom is called the nucleus. The nucleus is made up of particles called protons and neutrons. Electrons spin around the nucleus in shells. If the nucleus was the size of a tennis ball, the atom would be the size of a sphere about 1,450 feet in diameter, or about the size of one of the largest sports stadiums in the world. Atoms are mostly empty space.
If the naked eye could see an atom, it would look a little like a tiny cluster of balls surrounded by giant invisible bubbles (or shells). The electrons would be on the surface of the bubbles, constantly spinning and moving to stay as far away from each other as possible. Electrons are held in their shells by an electrical force.
The protons and electrons of an atom are attracted to each other. They both carry an electrical charge. Protons have a positive charge (+) and electrons have a negative charge (-). The positive charge of the protons is equal to the negative charge of the electrons. Opposite charges attract each other. An atom is in balance when it has an equal number of protons and electrons. The neutrons carry no charge, and their number can vary.
The number of protons in an atom determines the kind of atom, or element, it is. An element is a substance consisting of one type of atom. The Periodic Table of Elements shows elements with their atomic numbers—the number of protons they have. For example, every atom of hydrogen (H) has one proton and every atom of carbon (C) has six protons.
Electricity is the movement of electrons between atoms
Electrons usually remain a constant distance from the atom's nucleus in precise shells. The shell closest to the nucleus can hold two electrons. The next shell can hold up to eight. The outer shells can hold even more. Some atoms with many protons can have as many as seven shells with electrons in them.
The electrons in the shells closest to the nucleus have a strong force of attraction to the protons. Sometimes, the electrons in an atom's outermost shells do not have a strong force of attraction to the protons. These electrons can be pushed out of their orbits. Applying a force can make them shift from one atom to another. These shifting electrons are electricity.
Static electricity exists in nature
Lightning is a form of electricity. Lightning is electrons moving from one cloud to another or electrons jumping from a cloud to the ground. Have you ever felt a shock when you touched an object after walking across a carpet? A stream of electrons jumped to you from that object. This is called static electricity.
Have you ever made your hair stand straight up by rubbing a balloon on it? If so, you rubbed some electrons off the balloon. The electrons moved into your hair from the balloon. The electrons tried to get far away from each other by moving to the ends of your hair. They pushed against or repelled each other and made your hair move. Just as opposite charges attract each other, like charges repel each other.
Last reviewed: December 17, 2021
Electric Charge – Learn
What is Electric Charge?
Electric charge is understood by considering the structure of an atom. Atoms have a nucleus consisting of positively charged protons and neutral particles called neutrons. Orbiting the nucleus are negatively charged electrons, which are attracted to the positively charged nucleus. With electrostatic forces, like charges repel and unlike charges attract.
How do objects become charged?
Atoms are neutral. This is because in any atom there are equal numbers of electrons and protons. Protons are held tightly to the nucleus but electrons are easier to be removed as they are in a cloud surrounding the nucleus. When an atom loses an electron it develops a positive net charge; when it gains an electron, it develops a negative net charge. When an atom gains or loses an electron it is known as an ion.
How do we measure charge?
The net charge is often referred to as the elementary charge. The letter q is used to represent the amount of charge. The SI unit of charge is the coulomb (C), where one coulomb is the charge on
The total charge can be calculated by multiplying the number of elementary particles by their specific charge:
All electrically charged objects produce an electrostatic force on other objects that have an overall net charge. The electrostatic force causes like charges to repel and opposite charges to attract. The magnitude of the electrostatic force can be calculated using Coulomb’s law, which is discussed later.
If a neutral atom has gained an electron, how would we now describe this particle?
This particle is an ion with an overall negative net charge
How many electrons would make up a charge of -2.5C?
Example 3: What would happen if two positively charged objects were brought close together?
They would exert a repulsive force on each other and tend to move away from each other.
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Students will put a static charge on a strip of plastic by pulling it between their fingers. They will see that the plastic is attracted to their fingers. Students will be introduced to the idea that rubbing the strip with their fingers caused electrons to move from their skin to the plastic giving the plastic a negative charge and their skin a positive charge. Through these activities, students will be introduced to some of the characteristics of electrons, protons, and neutrons, which make up atoms.
Students will be able to explain, in terms of electrons and protons, why a charged object is attracted or repelled by another charged object. They will also be able to explain why a charged object can even be attracted to an uncharged object. Students will also be able to explain that the attraction between positive protons and negative electrons holds an atom together.
Download the student activity sheet, and distribute one per student when specified in the activity. The activity sheet will serve as the “Evaluate” component of each 5-E lesson plan.
Be sure you and the students wear properly fitting goggles.
Materials for Each Group
Materials for Demonstration