​Charges and Potential Energy

When forces are in action, you can be sure that energy is also involved.
Suppose you have a system that consists of two opposite charges and their interaction. If you pull the opposite charges away from each other, the potential energy of the system increases.

Potential Energy

You can understand this by comparing it to potential energy. When you lift an object higher above the ground, potential energy increases.
When you drop the object, the force of gravity pulls the object to the ground and its gravitational potential energy decreases.

As you apply a force to move opposite charges away from each other, the electrical potential energy of the system increases.
When the electric force between opposite charges pulls them together naturally, the

potential energy of the system decreases

Electric charges play a major role in daily life. Any time you use electricity, you are using energy from electric charges that are in motion. The charges flow through materials as water flows down a stream.
The continuous flow of charge is known as electric current. Current is measured as a rate in units called amps. The number of amps describes the amount of charge that passes by a given point each second.​

Current flows through paths known as circuits. A circuit is a path that runs in a loop. A basic electric circuit contains a source of energy connected with wires to a device that runs on electricity.
Current flows from the source of energy, through the wires, through the electric device, and back to the source.

Why do charges flow through a circuit?
They move because of differences in potential energy. Current flows from a point of higher potential energy to a point of lower potential energy in the circuit.
This difference in electrical potential energy per charge is called voltage. The voltage acts like a force that causes current to flow. Voltage is measured in units of volts. The abbreviation for this unit is V.

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​Voltage (V)

You can compare a charge in a circuit to gravity. When an object falls, the force of gravity pulls the object from a position of higher potential energy to a position of lower potential energy. You give that potential energy back when you lift the object up to its initial position. A battery gives energy back to charges as well. Inside the battery, the energy from chemical reactions is converted to electrical energy, which increases the potential energy of the electric charges.
Charges leave the battery through the high-potential terminal, move through the circuit, and return to the low-potential terminal.

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Some materials have electrons that are tightly bound to their atoms. Their electrons are difficult to move. Those materials, called insulators, do not allow charge to flow. Therefore, they have a high resistance to electric current. On the other hand, some materials have electrons that are more loosely bound to their atoms. Those materials are conductors—they allow charge to flow more freely

Just as there are conductors of heat, there are insulators and conductors of charge.

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Include rubber, wood, and glass

Insulators

include materials such as silver, copper, and gold.

Conductors