Glossary

Voltage: The force or "push" driving electrical energy through a conductor or wire that can be compared to the pressure of water in a pipe. Voltage is measured in volts (V) or kilovolts (kV = 1000 volts).

Current: The rate of flow of electrical energy through a conductor or wire, comparable to the amount of water flowing in a pipe. Electric current is measured in amperes or "amps" (A).

Field: A term used to describe the effect any object has on its surrounding space. For example, a temperature field exists near a hot object. Electric and magnetic fields are invisible lines of force surrounding any wire or electrical device carrying or using electricity. Fields are strongest near their source and decrease quickly with distance from the source.

Electric Fields: Produced by voltage in a conductor or wire. For example, a lamp or appliance (which is plugged in but not turned on) has an electric field. Generally, the higher the voltage, the higher the electric field. These fields can be shielded by buildings and other objects. Electric fields are measured in volts per meter (V/m) or kilovolts (1000 volts) per meter (kV/m).

Magnetic Fields: The product of current flowing in a conductor or wire. For example, a lamp that is turned on produces a magnetic field. Generally the higher the current, the higher the magnetic field. While electric fields can be shielded, magnetic fields are very difficult and expensive to shield, which usually makes this option impractical. Magnetic fields are measured in microtesla (mT) in Canada and most of the world or milligauss (mG) in the United States. Note: 1 mT = 10 mG.

Distribution Line: A power line used to distribute power in a local region. Main feeder or "primary" distribution lines typically operate at voltages between 4 kV (kilovolts) and 44 kV, levels much lower than the voltages of transmission lines. Secondary distribution lines supply electricity to residential, commercial and industrial users at levels of 120 V or 240 V. Currents from some distribution lines can be comparable to transmission line currents.

Transmission Line: A power line used to carry large quantities of electric power at high voltage, usually over long distances. In Ontario, transmission lines operate at voltages of either 115 kV, 230 kV or 500 kV. They are usually suspended from steel towers or large wooden poles.

back to top