Please tell me the function of relays

To write programs. Language is called Relay Ladder Logic. That's were the origin of "bug" in a program originated. The program didn't work because a real bug was stuck between two contacts.

To isolate electrical circuits.

To use a low power circuit to control a high power load.

Relays are used to allow one circuit to control another. Often a small current may be used to switch a larger one. They are also used to switch one circuit based on another, you can't start a motor unless what it drives has oil pressure or the cover is closed, etc.

Kiss,

Quote:

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Originally Posted by KeepItSimpleStupid

To write programs. Language is called Relay Ladder Logic. That's were the origin of "bug" in a program originated. The program didn't work because a real bug was stuck between two contacts.

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Ummm... what?

Software bug - Wikipedia, the free encyclopedia

The excerpt:
Problems with radar electronics during World War II were referred to as bugs (or glitches), and there is additional evidence that the usage dates back much earlier.
Photo of what is possibly the first real bug found in a computer.
Photo of what is possibly the first real bug found in a computer.

The invention of the term is often erroneously attributed to Grace Hopper, who publicized the cause of a malfunction in an early electromechanical computer. A typical version of the story is given by this quote:
“ In 1946, when Hopper was released from active duty, she joined the Harvard Faculty at the Computation Laboratory where she continued her work on the Mark II and Mark III. Operators traced an error in the Mark II to a moth trapped in a relay, coining the term bug. This bug was carefully removed and taped to the log book September 9th 1945. Stemming from the first bug, today we call errors or glitch's [sic] in a program a bug. [3]

Yes I am aware of this history , what does that have to do with the question? The other comments you made did answer the question.

Really does not matter, the poster is most likely taking an exam, and did not listen to the instructor or read the assignment.