31 Questions
What is the reason for using circuit control devices?
To control the flow of electricity in a circuit
Which of the following is a general type of circuit control device?
Switch
What is the difference between a manual and an automatic switch?
Manual switches require human intervention to operate, while automatic switches operate without human intervention
What is the reason for using multicontact switches?
To control multiple circuits with a single switch
How many possible positions does a single-pole, double-throw switch have?
2
What is the common name for an accurate snap-acting switch?
Micro-switch
What is the main purpose of circuit control devices?
To apply and remove power in a circuit
What was the early means for turning power on and off as practical uses for electricity were found?
Disconnecting a wire from a battery
What was the early experimenters' method for controlling power to their experiments?
Disconnecting a wire from a battery
What was used in the late 1700s and perfected by Morse in the 1830s to open and close the signal circuit?
Mechanically operated contact lever
What was the early form of circuit control devices known as?
Blade-and-jaw knife switch
What is the main function of modern circuit control devices?
To open and close a circuit
What was the beginning of circuit control devices?
Blade-and-jaw knife switch
What is the simplest form of circuit control?
'Turning on and off' power in a circuit
How did early experimenters control power to their experiments?
'Disconnecting' wires from a battery
Why was a convenient means for turning power on and off needed as practical uses for electricity were found?
To protect equipment and personnel from potential damage or danger
What is the difference between a single-pole, double-throw switch and a double-pole, double-throw switch?
The single-pole, double-throw switch has one pole and two positions, while the double-pole, double-throw switch has two poles and three positions.
Which of the following correctly describes a momentary switch?
A switch that remains in its operated position only as long as it is held in that position.
What is the main function of a solenoid in a circuit?
To provide mechanical movement when energized
What is the reason for using multicontact switches?
To allow for more complex control of a circuit by providing multiple input and output connections
What does a rocker switch refer to in the context of circuit control devices?
A switch that rocks back and forth to change its position
What is the purpose of a relay in a circuit?
To isolate the control circuit from the power circuit
What is the main purpose of circuit control devices?
To control the application and removal of power
What was the early means for turning power on and off as practical uses for electricity were found?
Using a clutch between a generator and a steam engine
What was the beginning of circuit control devices?
Disconnecting a wire from a battery
Why was a convenient means for turning power on and off needed as practical uses for electricity were found?
To prevent damage to the equipment or endangerment of personnel
What was used in the late 1700s and perfected by Morse in the 1830s to open and close the signal circuit?
Telegraph systems
What is the difference between a manual and an automatic switch?
Manual switches require human intervention, while automatic switches operate without human intervention
What is the common name for an accurate snap-acting switch?
Solenoid
What is the simplest form of circuit control?
Application and removal of power
How many possible positions does a single-pole, double-throw switch have?
4
Study Notes
- Circuit control devices are used in various fields where electrical or electronic circuits are present, including submarines, computers, aircraft, televisions, medical instruments, and more.
- Electricity was discovered before recorded history, but practical uses were not recognized until the late 18th century.
- Early methods of controlling electricity included disconnecting wires from batteries or using clutches between generators and steam engines.
- Telegraph systems used a mechanically operated contact lever for opening and closing circuits in the late 1700s and early 1800s.
- Early power switches were simple hinged beams arranged to open or close circuits.
- Modern circuit control devices can change resistance from a few milliohms to over 100,000 megaohms in milliseconds.
- Some devices only require a movement of.001 inch to open or close.
- Circuit control is needed to turn power on and off or open and close circuits.
- If a circuit develops problems that could damage equipment or endanger personnel, it should be possible to control the power.
- Circuit control devices include switches, solenoids, and relays.
- Switches change the flow of electricity when they are closed or opened. They have schematic symbols, different types (manual, automatic, multicontact, rocker, etc.), and various positions (single-pole, double-throw, etc.).
- Solenoids are electrically operated valves that control the flow of fluids. They have an operating principle and can be checked for proper operation through various methods.
- Relays are switches that use an electromagnetic force to open or close circuits. They come in different types (contact, mercury-wetted, reed, etc.) and can be checked for proper operation and serviced accordingly.
- Circuit control devices have current and voltage ratings, which determine the maximum amount of electricity they can handle.
- Two types of meters can be used to check switches: digital multimeters and clamp meters.
- Proper substitute switches can be selected from a list based on specifications.
- Preventive maintenance of switches includes checking conditions such as contacts, actuators, and insulation resistance.
- Solenoids operate based on the principle of a magnetic field, while relays use electromagnetic force to change the state of a circuit.
- Solenoids and relays can be checked for proper operation through methods such as visual inspection, electrical testing, or observing the effect on the controlled device.
- Relays can be serviced by cleaning, adjusting, or replacing parts as needed.
Test your knowledge of circuit control devices with this quiz based on Chapter 3 of the PDHonline course E247. Explore the reasons for using circuit control devices and the general types of circuit control devices.
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