The basic unit of matter is the atom, which is made up of protons, electrons, and other particles. Protons and electrons have a property called electric charge; electrons have a negative electric charge and protons have a positive electric charge. The charges interact and like charges repel and unlike charges attract.

Electrons can be moved and electrostatic charge, or static electricity, results from a surplus or deficiency of electrons.

A quantity of charge (q) is measured in units of coulombs (C), the charge equivalent to the transfer of 6.24 × 10¹⁸ charged particles such as the electron. The fundamental charge of an electron or proton is 1.60 × 10^-19 coulomb. The electrical forces between two charged objects can be calculated from the relationship between the quantity of charge and the distance between two charged objects. The relationship is known as Coulomb's law.

A flow of electric charge is called an electric current (I).Current (I) is measured as the rate of flow of charge, the quantity of charge (q) through a conductor in a period of time (t). The unit of current in coulomb/second is called an ampere or amp for short (A).

An electric circuit has some device that does work in moving charges through wires to do work in another part of the circuit. The work done and the size of the charge moved defines voltage. A volt (V) is the ratio of work to charge moved, V = W/q. The ratio of volts/amps in a circuit is the unit of resistance called an ohm. Ohm's law is V = IR.

Disregarding the energy lost to resistance, the work done by a voltage source is equal to the work accomplished in electrical devices in a circuit. The rate of doing work is power, or work per unit time, P = W/t. Electrical power can be calculated from the relationship of P = IV, which gives the power unit of watts.

Magnets have two poles about which their attraction is concentrated. When free to turn, one pole moves to the north and the other to the south. The north-seeking pole is called the north pole and the southseeking pole is called the south pole. Like poles repel one another and unlike poles attract.

A current-carrying wire has magnetic field lines of closed, concentric circles that are at right angles to the length of wire. The direction of the magnetic field depends on the direction of the current. A coil of many loops is called a solenoid or electromagnet. The electromagnet is the working part in electric meters, electromagnetic switches, and the electric motor.

When a loop of wire is moved in a magnetic field, or if a magnetic field is moved past a wire loop, a voltage is induced in the wire loop.The interaction is called electromagnetic induction. An electric generator is a rotating coil of wire in a magnetic field. The coil is rotated by mechanical energy, and electromagnetic induction induces a voltage, thus converting mechanical energy to electrical energy. A transformer steps up or steps down the voltage of an alternating current. The ratio of input and output voltage is determined by the number of loops in the primary and secondary coils. Increasing the voltage decreases the current, which makes long-distance transmission of electrical energy economically feasible.

Summary of Equations