Induced voltage is an electric potential created by an electric field, magnetic field, or a current. The induced voltage in natural and man-made material is carefully planned in many disciplines, including safety and equipment protection. In the early history of electricity, Benjamin Franklin demonstrated the buildup of electrical charges in clouds that resulted in electrostatic charging and slight luminescence of certain material.
Friction between air and cloud particles creates electrostatic charge buildup in clouds. The voltages generated in clouds at elevated altitudes can reach far beyond billions of volts. When the atmospheric conditions build a lower-resistance path between the charged cloud and the ground, lightning strikes where most of the energy reaches the ground. The high current associated with a lightning strike is conducted to the ground by an ionized section of the atmosphere, and this can easily induce voltages in conductive material such as steel towers and electrical cabling. The result is current-induced voltage that may damage sensitive electronic equipment.
Field-induced voltage is created by either an electric or magnetic field. A voltage-induced electric field is when a capacitor or condenser is charged with a direct current and a positive charge on one plate and a negative charge on the other plate are induced. The same capacitor will have a voltage across its terminals, and this is field-induced voltage. In voltage alteration, the resulting current flow changes voltage level. When lightning discharges a cloud formation, the extremely high voltage that has previously caused the lightning decreases to a certain level determined by air and ground conditions.
This voltage may further create a magnetic field, thus it may be referred to as an induced voltage magnetic field. When lightning hits the lightning arrestor on top of a radio tower, the current surge travels toward the ground on the grounding cable. This current generates a transient magnetic field that may induce a voltage on any nearby conductor. The transformation may recur as extensively as the intensity of the original energy allows. This may suggest why the damage to equipment due to current and voltage surges during lightning storms can be extensive.
In an electrical transformer, the primary winding induces a voltage across the secondary winding. The induced voltage formula suggests that the ratio of the output to input voltage is equal to the ratio of the number or turns on primary to that of the secondary winding. Additionally, the voltage test on a transformer uses a voltmeter connected to the input terminals and later to the output terminals of the transformer. By comparing the two readings, it is possible to calculate the ratio of turns.