Understanding Electrical Terms 

serving the Ottawa area for over 30 years!

KEY CONCEPTS

  • Electrical terms
  • More on voltage
  • Current flow

You will come across terms and units used regularly in the electrical trade. The following electrical trade terms are used throughout the website.

CIRCUIT

A closed path for current to pass through is called a circuit. It consists of a voltage source, connecting conductors and a load. There are only two types of circuit connections: series and parallel.

Series: This is a type of circuit in which the flow from the supply to the load and back to the supply only follows one path. Think of it like a garden hose: the water flows in one end and has no choice but to travel to the other end of the tube before it can escape.

Parallel: This type of circuit is one in which the flow can take several paths. Compare this to a sprinkler. This type has many holes for water to escape.

There are also combination circuits which contain both series and parallel paths.

Open circuit: This describes a circuit that is broken or an incomplete path. Exercise care with this term. To many people “open” means to turn “on” such as a tap. In the electrical trade “open” means the opposite, to stop the flow. Electrons or electricity cannot flow if the circuit is open. For power to flow, a completed circuit or a circuit that is closed must exist. At any point where the completed circuit is broken or opened, the circuit electron flow ceases.

Short circuit: Short circuits are circuits with low resistance. The term ‘short circuit’ does not refer to the length of the circuit. It is purely a description of low resistance; so low that a current of dangerous proportion can flow.

Short circuits are hazardous: they cause fires, blow fuses, and open circuit breakers. Most manufacturers consider a short circuit as any situation that will allow ten times the rated current of a circuit to flow. Consider the example of a 15 A circuit, such as a typical lighting circuit in residence. If the resistance were low enough to allow 150 A to flow, this would constitute a short circuit. This current should immediately open the fuse or breaker.

DIRECT CURRENT

Direct current (DC) flows through a circuit which occurs in only one direction. DC is in straightforward electrical circuits where the electron flow moves from the positive end of the circuit to the negative one.

ALTERNATING CURRENT

Most houses and businesses use alternating current (AC) rather than direct current. Alternating current changes its direction in a back-and-forth direction, alternating from 50 to 60 times per second. Different countries set individual values for the number of alterations per second. Alternating current allows the voltage to be changed quickly and therefore makes it more convenient for long-distance transmission than direct current electricity. Alternating current also permits the installation of inductors and capacitors in electronic circuitry.

In North America, alternating current is 60 Hertz (Hz). Hz means cycles per second; thus, 60 Hz means 60 cycles per second. The alternating current, created by a generator, comes as waves of electricity. These waves are produced inside alternators by sweeping conductors through a uniform magnetic field causing induction or induced voltage to be created. The resulting waveform is based mathematically on the function of sine. This function describes the action of a clock pendulum and the ocean tides. A recurring pattern, first in one direction, then the other, has two halves or alternations in each cycle. In the electric circuit, this pattern occurs 60 times each second. This may seem fast, but think of the FM radio dial: These waves repeat 108 M Hz. This is one hundred and eight million cycles per second. Compared to this, 60 cycles is quite slow! Any cycle that repeats in one second is a Hz.

CURRENT FLOW

The ampere (A) is the intensity of the current flow. Current is a common term most laypersons understand. The 15 A fuse or circuit breaker is the most common protective device used in-home wiring. This is compatible with the 14 AWG wire size normally used in houses. Today we recognize that two types of current flow exist: electron flow and conventional flow. Each one has a different explanation of the movement of current.

Electron theory is based on the fact that like charges repel, while unlike charges attract. Electrons are negatively charged particles and therefore move through a circuit from the negative terminal to the positive one. In other words, with electron flow, current flows from negative to positive. This is the theory that underpins the work of most electricians.

The conventional theory is the opposite. Current flows from positive to negative. This theory is based on atomic knowledge. It has been proven that electrons move at a rate of only 17 cm per minute! This would lead to the premise that since electricity or energy transfer occurs at the speed of light, possibly faster, that the electron is only the carrier or medium through which energy is transferred. Energy moves opposite the physical medium or positive to negative. This is the theory that underpins the work of many mechanics, such as those who repair cars.

When inspecting electrical work in a home, you do not need to concern yourself with electron or conventional theory; you need to understand the outcome of voltage, current, resistance, and power. Regardless of the theory used the outcome is the same.

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