Electronic Switches and Their Types

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Questions and Answers

What is the primary purpose of an electrical switch?

To generate electricity

To interrupt the flow of electrons in a circuit (correct)

To store electrical energy

To regulate voltage

Which of the following best represents a characteristic of process switches?

They only operate at high voltages

They are used solely for lighting applications

They are designed for specific operational conditions (correct)

They have a universal voltage rating

What does the term 'normal' state refer to when discussing switch contacts?

The lifetime duration of a switch

The emergency position of a switch

The maximum current a switch can handle

The default position of a switch before it is activated (correct)

Which section of the document would you find information about electrical switch types?

Switch Types Signup and view all the answers

What does 'pole and throw' refer to in switch terminology?

The number of circuits a switch can control Signup and view all the answers

In the context of electrical symbols, what does generic symbology refer to?

Standardized symbols representing various electrical components Signup and view all the answers

Which objective focuses on the understanding of switch types and contacts?

To understand type, process and contacts of switches Signup and view all the answers

What is the significance of the review section in the document?

It summarizes the key points of the content covered Signup and view all the answers

What feature distinguishes pushbutton switches that stay in their 'in' position?

They have a mushroom-shaped button for easy push-pull action. Signup and view all the answers

How do selector switches differ from toggle switches?

Selector switches can be operated with a rotary knob or lever. Signup and view all the answers

What is a primary use of joystick switches?

To provide fluid movement in crane and robot controls. Signup and view all the answers

What type of switch is designed to operate based on machine motion?

Limit switch Signup and view all the answers

Which type of limit switch is equipped with a lever actuator?

Lever actuator limit switch Signup and view all the answers

What does a proximity switch detect?

The approach of metallic machine parts. Signup and view all the answers

Which feature is NOT typical of joystick switches?

Operated solely by the pushing action. Signup and view all the answers

What is the primary function of limit switches in machinery?

To prevent machine parts from moving too far. Signup and view all the answers

What is the primary function of the Nuclear Level Switch described?

To monitor the level of solid or liquid material in a vessel Signup and view all the answers

How does the radiation from the source affect the detector?

Decreased radiation triggers a relay mechanism Signup and view all the answers

Which type of contacts will connect the circuit when a relay is activated?

Normally-open (NO) contacts Signup and view all the answers

What is true about the radioactive sources used in the Nuclear Level Switch?

They pose no immediate health threat to personnel Signup and view all the answers

Why is it necessary to intelligently match switches to their tasks?

To achieve efficient and reliable operation Signup and view all the answers

What is the purpose of the relay mechanism in the context of the Nuclear Level Switch?

To provide a switch contact for measurement or alarms Signup and view all the answers

Which statement about the arrangement of the radioactive source and detector is correct?

They are mounted outside the vessel across its diameter Signup and view all the answers

What is a common characteristic of Normally-closed (NC) contacts?

They disconnect the circuit when the relay is activated Signup and view all the answers

How does the brass bulb switch mechanism operate?

The gas or liquid inside the bulb expands with heat, generating pressure. Signup and view all the answers

What role does conductivity play in a liquid level switch?

It allows the liquid to carry a current between two metal probes. Signup and view all the answers

What is a common design for detecting solid materials in a storage bin?

A small paddle wheel that stops turning. Signup and view all the answers

What triggers a flow switch when detecting liquid or gas flow?

A paddle or vane is pushed by the flow above a threshold. Signup and view all the answers

Why is it usually impractical to switch full load current through a conductive liquid in liquid level switches?

It poses safety risks and can be dangerous. Signup and view all the answers

How does a tuning fork level switch operate?

It dampens vibration amplitude when material fills the bin. Signup and view all the answers

What is a differential pressure switch in a flow detection system designed to measure?

The pressure drop across a restriction in the pipe. Signup and view all the answers

What type of materials can level switches detect in addition to liquids?

Solid materials such as wood chips and coal. Signup and view all the answers

What does a normally-open switch signify in its schematic representation?

An open connection ready to close Signup and view all the answers

Which of the following best describes a normally-closed switch?

Closed in its normal state and opens when actuated Signup and view all the answers

In generic symbology, how are normally-closed contacts represented?

With a diagonal line bridging between the two lines Signup and view all the answers

What is a common visual characteristic of a normally-open switch in control logic schematics?

Vertical lines that do not touch Signup and view all the answers

Which of the following statements about switch representations is true?

The symbol for switches varies according to their purpose Signup and view all the answers

What should not be confused with the symbol of a normally-open switch?

The symbol of a capacitor Signup and view all the answers

What does the schematic representation of a capacitor ensure?

It clearly distinguishes it from any switch contacts Signup and view all the answers

Which of these symbols would signify a normally-open switch in a control logic schematic?

Two vertical lines not touching Signup and view all the answers

Study Notes

Switches

A switch is an electronic device that interrupts the flow of electrons in a circuit.
Pushbutton switches can be latched on or off with every push or remain in the "in" or "pressed" position until the button is released.
Selector switches use a rotary knob or lever to select one of multiple positions.
Joystick switches use a lever that can move in multiple directions, and activate contact mechanisms based on the direction and force of the lever motion.

Process Switches

Process switches are designed to be operated by the motion of a machine, rather than by human interaction.
Limit switches are specifically used to limit the motion of a machine by stopping its actuating power if it moves too far.
A lever actuator limit switch has a lever tipped with a roller bearing.
Proximity switches detect the approach of a metallic machine part using a magnetic or electromagnetic field.
Temperature switches use a brass bulb filled with liquid or gas, which expands and generates pressure as it heats up, activating the switch mechanism.
Liquid level (float) switches use a floating object that activates a switch mechanism when the level of liquid rises above a certain point.
Liquid level (float) switches can also detect the level of solid materials like wood chips, grain, coal, or animal feed.
Liquid flow switches detect gas or liquid flow rates above a certain threshold using a paddle or vane.
Flow switches can also be constructed as differential pressure switches, measuring the pressure drop across a restriction in the pipe.
Nuclear switches use radioactive source material and a radiation detector to detect liquid or solid material levels by measuring the attenuation of radiation.

Pole and Throw

The number of contacts on a switch is referred to as the number of "poles".
The number of "throws" refers to the number of positions a contact can be thrown to.
Normally-open (NO) contacts connect the circuit when the relay is activated and disconnect it when inactive.
Normally-closed (NC) contacts disconnect the circuit when the relay is activated and connect it when inactive.

Generic Symbology

Generic switch contact designation uses vertical lines to represent contact points.
Normally-open contacts are represented by lines not touching, while normally-closed contacts are represented by lines connected with a diagonal line.
The capacitor symbol in control logic diagrams uses a single vertical line to represent the capacitor to clearly distinguish it from a normally-open switch contact.

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Description

This quiz covers various types of electronic switches, including pushbutton, selector, joystick, and process switches. You will learn about their functionalities, applications, and mechanisms. Test your knowledge on limit switches, proximity switches, and temperature switches.