Fundamental Principles of Electricity: Voltage and Current

Understanding Voltage and Potential Difference

Voltage: The voltage that a generator is capable of providing is the energy transferred to each coulomb of charge to traverse the circuit. It is represented by the letter V and is measured in volts.

One volt (V) is equal to one joule per coulomb. That is, a generator of 220 volts, for example, is capable of providing an energy of 220 joules to each coulomb of charge. The formula is: 1 volt = 1 joule / 1 coulomb.

Current Intensity and Amperes

Current intensity: The intensity of an electrical current is defined as the amount of electric charges passing through a section of the conductor in a given time. This quantity is represented by the letter I, and is measured in amperes.

One ampere (A) equals one coulomb per second. The formula is: 1 ampere = 1 coulomb / 1 second.

Electrical Resistance and the Ohm

Resistance: Electrical resistance is the greater or lesser ability of a material to allow the passage of electrical current. It is measured with an ohmmeter and is expressed in ohms.

A resistance of one ohm is presented by a conductor when it allows an electric current of one ampere to pass while the voltage is one volt.

Direct Current (DC) vs. Alternating Current (AC)

Electrical power provided by batteries always runs in the same direction, from the negative to the positive terminal; this is known as Direct Current (DC). By contrast, the current that comes into our homes via the electricity network changes direction 100 times each second; this is known as Alternating Current (AC).

The difference between them is due to the way they are generated. In the first case, the flow comes from chemical reactions taking place between substances from which batteries are manufactured. In the second case, the current is obtained by exploiting the phenomenon of electromagnetic induction.

How Alternators Generate Electricity

Alternators are devices that generate alternating current. The simplest alternator comprises a magnet moving periodically in and out of a coil. All alternators are composed of two main elements:

• The Rotor: Which can be a magnet or an electromagnet.
• The Armature Coil: Which is always connected to an external circuit.

At the ends of the wire forming the coil, components called thin rings are connected. These are in contact with a brush to collect the electricity and allow the reel to rotate freely.