Inductors

Inductance Electrons in motion create electromagnetic fields – Recall from previous section that electrons in motion also create an electrostatic field The electromagnetic field can be intensified by making a loop in the wire A device which creates an electromagnetic field is called an inductor

Inductors Schematic symbol for inductor or coil

Inductance The unit of measure of inductance is henry The inductor is an electromagnet One use of the inductor is in relays to operate a switch Another use is in the construction of electric motors

Relays Contacts

Relays M 12 volts 760 volts

Relays M

M

Inductors

Three factors affecting inductance – Nature of the coil Size Diameter of conductor Number of turns Length – Current flow – Presence of materials within the magnetic field

Variable Inductor

Inductors When current is turned off from electromagnet, the electromagnetic field collapses back to the coil There is a charge or current present on the inductor Electromagnetic energy is stored in inductors Inductors are used to convert AC to DC

Inductors 0 volts 10 volts Time “on” “off” “on” “off” Capacitor Inductor

Inductors Energy is expended in forming electromagnetic field Inductors resist current flow – electrons resist flow Impedance is reluctance in a coil Three factors affecting inductance also affect impedance

Transformers Transformers are constructed from two inductors or coils in close proximity to one another Just like capacitors, current can be induced to flow in the secondary coil if enough current flows through the primary Transformers are used to increase or decrease current flow and/or voltage

Transformers Primary Secondary

Transformers Step up transformers have more turns in the secondary coil and increase output Step down transformers have fewer turns in the secondary and decrease output Isolating transformers have same number of turns in both coils and neither decrease nor increase output – but isolate two segments of a circuit

Transformers