Beatrice Lang
An electric switch is a component that can connect or disconnect the electrical path in a circuit, thereby controlling the flow of electricity. The most common type of switch is an electromechanical device with one or more sets of movable electrical contacts connected to external circuits. When the switch is pressed, the contacts come into contact, closing the circuit and allowing the flow of electricity. When the switch is not pressed, the contacts are separated, opening the circuit and stopping the flow of electricity. The switch's role is to alter a circuit's electrical characteristics to control electron movement, and it is an essential component in any electrical setup.
| Characteristics | Values |
|---|---|
| Definition | A device that connects or breaks a circuit, allowing electrical flow to be started or stopped. |
| Types | Single-pole, single-throw (SPST); Single-pole, double-throw (SPDT); Toggle; Push-button; Momentary; Normally Open; Normally Closed; Circuit Breaker; Dimmer; Mercury or "silent"; Oil; Switchgear; etc. |
| Function | Turns electric circuits on and off, or switches electric circuits. |
| Operation | Can be operated manually (e.g. light switch, keyboard button) or automatically (e.g. sensing element). |
| Actuation Force | The force required to physically operate a switch, e.g. by pressing a button or pulling a lever. |
| Environmental Protection | Certain electrical switches are designed to withstand harsh environmental conditions, such as extreme heat or cold, moisture, and dust. |
| Current Rating | The maximum electric current that the switch is designed to carry. |
| Voltage Rating | The maximum voltage that the switch is designed to withstand. |
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What You'll Learn
- Electric switches can be manually operated, like a light switch, or function as a sensing element to sense the position of a machine part, liquid level, pressure, etc
- They can be categorised as momentary or alternate switches
- They are made of various components, including actuators, toggles, and contacts
- They can be classified as normally open or normally closed switches
- They are rated by the maximum current and voltage they can withstand
Electric switches can be manually operated, like a light switch, or function as a sensing element to sense the position of a machine part, liquid level, pressure, etc
An electric switch is a device that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. Electric switches can be manually operated, like a light switch, or can function as sensing elements to sense the position of a machine part, liquid level, pressure, etc.
Wall switches or light switches are the most common examples of manually operated electric switches. They are installed in wall-mounted outlet boxes and used to control the flow of electricity to light fixtures or electrical outlets. The classic design is the simple toggle-lever switch, but there are also rocker switches, push-button switches, and dimmer switches. When the switch lever is flipped, the inner gateway inside the switch body opens or closes the circuit pathway, allowing or interrupting the flow of electricity.
Electric switches can also function as sensing elements in various applications. For example, pressure switches are a type of switch that senses changes in fluid pressure and activates electrical contacts when a set pressure is reached. They are used to regulate pressure in systems or maintain stable reservoir levels, as well as to safeguard equipment. Pressure switches consist of components such as diaphragms, pistons, or Bourdon tubes that detect and respond to pressure changes.
Another example of a sensing element is a vacuum pressure switch, which measures the vacuum or negative pressure in a system. These switches are commonly found in boilers, electric heaters, and transmission systems. Additionally, pressure-sensitive mats used to automatically open doors in commercial buildings are also a form of pressure switch that detects mechanical force.
The versatility of electric switches, whether manually operated or functioning as sensing elements, makes them integral components in a wide range of applications, from residential lighting to industrial equipment control.
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They can be categorised as momentary or alternate switches
An electric switch is a device that can connect or disconnect the conducting path in an electrical circuit, thereby interrupting, diverting, or continuing the electric current. Switches are used to turn electric circuits on and off. They are usually operated manually, but can also function as sensing elements.
Switches can be categorised as momentary or alternate switches. A momentary switch is a self-reset type of switch, which stays on only when its button is pressed and held. When the button is released, the switch returns to its off state. Examples of the momentary operation type include the buttons on crane game machines in amusement facilities and buzzers for disembarking from a bus.
On the other hand, an alternate switch is a self-holding type of switch. It turns on when its button is pressed and maintains its on state even after the button is released. The switch turns off when the button is pressed again. An example of an alternate switch is the power switch on a TV. Alternate switches are used to maintain the on state for a long period, such as for main power switches.
The number of "poles" and "throws" are also used to describe switch contact variations. The number of poles refers to the number of electrically separate switches that can be controlled by a single physical actuator. The number of throws refers to the number of separate wiring path choices other than "open" that the switch can adopt for each pole. A single-throw switch has one pair of contacts that can either be closed or open, while a double-throw switch has a contact that can be connected to either of two other contacts.
In summary, the key difference between momentary and alternate switches lies in their behaviour after being activated. A momentary switch only stays on while it is being activated (e.g. a button being pressed), whereas an alternate switch remains on even after the activation action has ceased.
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They are made of various components, including actuators, toggles, and contacts
An electric switch is a device that can open and close electrical circuits, thereby interrupting or diverting the electric current. The most common type of switch is an electromechanical device consisting of one or more sets of movable electrical contacts connected to external circuits. These contacts are a crucial component of an electric switch. When a pair of contacts is touching, a current can pass between them; when they are separated, no current can flow.
Switches are made in many different configurations. They may have multiple sets of contacts controlled by the same knob or actuator, and the contacts may operate simultaneously, sequentially, or alternately. The actuator is a moving part that applies the operating force to the contacts. It is a component of an electrical switch that’s used to control the flow of electrons in a circuit and its mechanics. In other words, it is responsible for closing and opening the circuit. There are different types of actuators, including toggle, rotary, and biased. A toggle actuator, for example, features a lever that is engaged manually. When the lever is pulled, the switch opens or closes, depending on its design. Rotary actuators, on the other hand, are characterized by a handle that is twisted to open or close the circuit.
The word "toggle" refers to a mechanism or joint consisting of two arms, which are almost in line with each other, connected with an elbow-like pivot. Toggle switches are manually actuated by a mechanical lever, handle, or rocking mechanism. They are available in many different styles and sizes and are used in numerous applications. Toggle switches may be mechanically interlocked to prevent forbidden combinations. The term "toggle" is also used more broadly to refer to any switch with a short handle and a positive snap-action, even if it does not contain a toggle mechanism.
In addition to actuators and contacts, the terms pole and throw are used to describe switch contact variations. The number of poles refers to the number of electrically separate switches controlled by a single physical actuator. Meanwhile, the number of throws indicates the number of separate wiring path choices other than "open" that the switch can adopt for each pole. For example, a single-throw switch has one pair of contacts that can be either closed or open, while a double-throw switch can connect to either of two other contacts.
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They can be classified as normally open or normally closed switches
An electric switch is a device that can connect or disconnect an electrical circuit, thereby interrupting or diverting the electric current. The most common type of switch is an electromechanical device consisting of one or more sets of movable electrical contacts connected to external circuits.
Switches can be classified as normally open or normally closed, depending on their default state. In other words, this classification depends on whether the switch contacts are open or closed when there is no external influence.
A normally open (NO) switch is characterised by its default open state. In its resting position, the switch keeps the circuit open, preventing the flow of electric current. When activated, usually by pressing or toggling, the current can pass through by closing momentarily. This configuration is commonly used for safety or control applications where a circuit must remain inactive until deliberately activated. For example, a normally open switch is used for a doorbell, which only rings when you push the button, closing the circuit. Other applications include start buttons, reset buttons, and emergency stop buttons in industrial settings.
On the other hand, a normally closed (NC) switch allows uninterrupted current flow by maintaining a closed circuit. It temporarily opens when an external force or triggering mechanism is applied, interrupting the circuit. This design ensures that the connected device or system operates continuously unless the operator intervenes. Activating a normally closed switch can cut all power to a machine, and they are often used in stop buttons and control circuits.
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They are rated by the maximum current and voltage they can withstand
An electric switch is a device that can connect or disconnect electrical circuits, thus interrupting or diverting the electric current. They are typically operated manually, such as a light switch or a keyboard button. Switches are made in many different configurations and can be further categorised by their size, robustness, and environmental resistance, among other characteristics.
Switches are rated by the maximum current and voltage they can withstand. This rating is crucial for understanding the switch's capabilities and limitations. When a switch is closed, it must not conduct a current higher than its rated current. Similarly, when the switch is open, the voltage across the switch must not exceed its voltage rating. These current and voltage ratings do not indicate a power rating, as a switch experiences either voltage or current flow, but not both simultaneously.
The ratings on a switch, such as "3A 250VAC" and "5A 125VAC", denote the maximum current and voltage the switch can handle. For example, a switch rated at 3A can conduct a maximum current of 3 amperes, while a rating of 250VAC indicates it can withstand a maximum voltage of 250 volts of alternating current. It is important to select a switch with appropriate ratings for the intended circuit to ensure safe and proper functioning.
The number of "poles" and "throws" are additional terms used to describe a switch's configuration. The number of poles refers to the number of separate switches controlled by a single actuator, while the number of throws indicates the wiring path choices available for each pole. For instance, a single-throw switch has one pair of contacts, while a double-throw switch can connect to two other contacts.
In summary, electric switches are rated by the maximum current and voltage they can safely withstand, and these ratings are essential for matching switches to the appropriate circuits.
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Frequently asked questions
An electric switch is a device that can connect or break a circuit, allowing electrical flow to be started or stopped.
An electric switch responds to an external force to mechanically change an electric signal. When the switch is pressed, the contacts come into contact, closing the circuit and allowing the current to flow. When the switch is not pressed, the contacts are separated, breaking the circuit and stopping the flow of electricity.
There are many different types of electric switches, including toggle, push-button, momentary, normally open, normally closed, and dimmer switches.
The main components of an electric switch are the actuator or toggle, which is the part that is physically operated, and the contacts, which are the conductive elements that make or break the electrical connections.
