Neets Module 3 Assignment 3
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What are three reasons circuit control is needed?
- To remove power from a malfunctioning device
- To remove power from a device you wish to work on and restore power when the work is completed
- To turn devices on and off as the device is needed
- To select the function or circuit desired within a device.
What are the three types of circuit control devices?
What is the difference between a manual and an automatic switch?
- A manual switch must be turned on or off by a person.
- An automatic switch turns a circuit on or off without the action of a person (by using mechanical or electrical devices).
What is one example of a manual switch?
A light switch, an ignition switch, television channel selector, etc.
What is one example of an automatic switch?
A thermostat, an automobile distributor, a limit switch, etc.
Why are multicontact switches used?
Multicontact switches make possible the control of more than one circuit or the selection of one of several possible circuits with a single switch.
What classification of a switch is used when you describe it as a rocker switch?
The type of actuator.
In describing a switch by the number of positions of the actuator, what are the two possible configurations for a single-pole, double-throw switch?
Two-position and three-position.
What type of switch should be used to control a circuit that requires a temporary actuation signal?
A momentary switch.
What type of switch is used if it is necessary to guard against a circuit being accidentally turned on or off?
A locked-position switch.
What is the common name used for an accurate snap-acting switch?
What is the current rating of a switch?
The maximum current a switch is designed to carry.
What is the voltage rating of a switch?
The maximum voltage allowable in the circuit in which the switch is installed.
What two types of meters can be used to check a switch?
An ohmmeter and a voltmeter.
If a switch must be checked with power applied, what type of meter is used?
What should you check when performing preventive maintenance on a switch?
The switch operation for smooth and correct operation, the terminals for corrosion, and the physical condition of the switch.
What is the operating principle of a solenoid?
The magnetic field created in a coil of wire and core will attract a soft iron plunger when current flows through the coil.
What is one example of the use of a solenoid?
A starter motor and solenoid.
If a solenoid is not operating properly, what items should be checked?
The connections, the plunger, the mechanism that the solenoid actuates, the energizing voltage, and the coil of the solenoid.
What is the operating principle of a relay?
The magnetic field created in a coil of wire will attract aft armature causing a movement in sets of contacts.
How does a relay differ from a solenoid?
The solenoid provides a mechanical movement of a plunger (a moveable core) while the core of a relay is fixed.
What are the two classifications of relays?
Control relays and power relays (contactors).
How can you determine if a relay is operating (changing from one position to the other)?
- By observing the movement of the contacts if the relay is open or sealed with a transparent cover.
- If the relay has an opaque cover, you can "feel" the operation of the relay by placing your finger on the cover.
What items should be checked on a relay that is not operating properly?
- The coil should be checked for opens, shorts, or a short to ground
- Terminal leads should be checked for charred or burned insulation
- The contact surfaces should be checked for film, carbon, arcing, and contact spacing.
What is used to clean the contacts of a relay?
A burnishing tool.
What tool is used to set contact clearances on a relay?
A point bender
What would you like to do?
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