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Switch:
An electric switch or a key is connected to the circuit to stop or allow the current flow.
![switch.png](https://resources.cdn.yaclass.in/80d620cc-5dee-4968-9769-304880999846/switchw200.png)
A toggle switch
The symbol for the switch is shown below:
![switch-w422.png](https://resources.cdn.yaclass.in/ed778197-f06c-4199-851c-693f099db994/switchw422w300.png)
Symbol of a switch
If a key is switched off (open), the current will not flow across the circuit; thus, it is an open circuit. A lamp does not glow in this type.
If the key is switched on (closed), the current will flow, making it a closed circuit. A lamp glows in this type.
If the key is switched on (closed), the current will flow, making it a closed circuit. A lamp glows in this type.
![shutterstock_1707749467.jpg](https://resources.cdn.yaclass.in/edcb9b77-178e-40f2-9b00-0a40f41dfa15/shutterstock1707749467w400.jpg)
Open and closed circuits
Ammeter:
An ammeter is an instrument used for measuring electric current in a circuit. The electric current is measured in the units of ampere.
![136910945444f0b389176b.jpg](https://resources.cdn.yaclass.in/ecbebfee-32ef-413f-b866-2cf5f256ee01/136910945444f0b389176bw200.jpg)
An ammeter
![Ammeter.png](https://resources.cdn.yaclass.in/3302a014-3f16-45fe-8718-497e7dbb5081/Ammeterw200.png)
Symbol of ammeter
Voltmeter:
A voltmeter is an instrument used for measuring the potential difference in a circuit. The potential difference is measured in the units of volts.
![Voltmeter_in_classroom.jpg](https://resources.cdn.yaclass.in/bb3f7820-6162-4c29-80c4-de5bb1c751ea/Voltmeterinclassroomw200.jpg)
A voltmeter
![Voltmeter_symbol.png](https://resources.cdn.yaclass.in/896abfdb-88bd-4f34-8b18-6db1dd89f675/Voltmetersymbolw200.png)
Symbol of voltmeter
Galvanometer:
A galvanometer is an instrument used to find the direction of the current.
![Galvanometer_-_001.jpg](https://resources.cdn.yaclass.in/de1ed26a-03e0-4789-8981-569c6481ddb2/Galvanometer001w200.jpg)
A galvanometer
![galvanometer.png](https://resources.cdn.yaclass.in/a013810b-6a0f-4d26-8a5c-990249ee9a65/galvanometerw200.png)
Symbol of galvanometer
Resistor:
The resistor is used to control the amount of current flowing through the circuit. The resistor can be fixed or variable.
Fixed resistor:
A fixed resistor has a definite or a fixed value that cannot change.
![rsamurti-RSA-IEC-Resistor-Symbol.png](https://resources.cdn.yaclass.in/a73c62a7-18ec-486d-91c5-ffd9be605265/rsamurtiRSAIECResistorSymbolw200.png)
Symbol of a fixed resistor
Variable resistor:
A variable resistor or a rheostat controls and selects the amount of current flowing through a circuit.
![rsamurti-RSA-IEC-Variable-Resistor-Symbol-1.png](https://resources.cdn.yaclass.in/10831d55-78a5-4308-b41b-1337ac871fc8/rsamurtiRSAIECVariableResistorSymbol1w200.png)
Rheostat
The components such as a diode, Light Emitting Diode (LED), seven-segment display and various other connections will be discussed in detail in upcoming sections.
Reference:
https://upload.wikimedia.org/wikipedia/commons/d/da/Ammeter.png
https://upload.wikimedia.org/wikipedia/commons/5/59/Voltmeter_symbol.png
https://upload.wikimedia.org/wikipedia/commons/6/67/Voltmeter_in_classroom.JPG
https://upload.wikimedia.org/wikipedia/commons/8/8a/Galvanometer_-_001.jpg
https://www.flaticon.com/free-icon/galvanometer_114771
https://freesvg.org/img/rsamurti-RSA-IEC-Resistor-Symbol.png
https://freesvg.org/img/rsamurti-RSA-IEC-Variable-Resistor-Symbol-1.png