Title: Solenoids and Relays
Description: In many electrical circuits it is necessary to change electrical power into mechanical motion. For example, a solenoid is used to engage the starter when the starter key is closed. The solenoid is designed to change electrical power into mechanical motion. Also, a relay is similar to a solenoid only it is uses low current to control another circuit with higher current. It is also designed to change electrical power into mechanical motion. To see how a solenoid or relay operates, refer to the electrical circuit on the left. Solenoids and relays operate on the principle of electromagnetism. When a wire is wrapped into a coil and electricity is passed through the wire, an electromagnet is produced. This electromagnet has both a north and a south pole. If a metal core in placed inside the coil of wire, the magnetism at the north and south poles becomes stronger.
Description: In many electrical circuits it is necessary to change electrical power into mechanical motion. For example, a solenoid is used to engage the starter when the starter key is closed. The solenoid is designed to change electrical power into mechanical motion. Also, a relay is similar to a solenoid only it is uses low current to control another circuit with higher current. It is also designed to change electrical power into mechanical motion. To see how a solenoid or relay operates, refer to the electrical circuit on the left. Solenoids and relays operate on the principle of electromagnetism. When a wire is wrapped into a coil and electricity is passed through the wire, an electromagnet is produced. This electromagnet has both a north and a south pole. If a metal core in placed inside the coil of wire, the magnetism at the north and south poles becomes stronger.
If a metal core were placed in the center of the coil, the metal core would also magnetically center itself. This is shown in the circuit to the left. When the switch is open, the metal core is being pulled to the right by a spring. However, if the switch were closed, the electromagnetic field that is produced would pull the metal core the left until it is magnetically centered. When the switch is opened again, the spring will pull the metal core out to the right again. This is how electrical power can be used to mechanically move something such as an on/of switch.
Relationship to Street Rods: As mentioned above, a solenoid is used to engage a starter. Referring to the drawing on the left, when the switch is opened, the center metal core or plunger is moved down by a spring (not shown). However, when the switch is closed the electromagnetism moves the metal core upward and tries to center the plunger. As it moves upward, the round disc on the top makes contact with another circuit, (acting like a switch) in this case energizing another circuit, the starter motor. All relays or solenoids operate based on these principles. Examples include the cooling fan relay, compressor relay, fuel injector solenoids, horn relay, starter solenoid, etc.
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