A question about relay

  • Thread starter Syndy
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[PLAIN]http://[url=http://postimg.org/image/pwudznwxd/][PLAIN]http://s16.postimg.org/pwudznwxd/image.jpg [Broken] [Broken] Hello everyone,

I'm new to this forum. I'm glad that there is a forum for physics as there are questions that I try to solve but to no avail , I hope to find the answer here.
I study IGCSE and yesterday I was doing a past paper exam and I couldn't agree with the answer in the mark scheme of one of the questions.

I know that the function of the relay is to switch on a circuit with powerful current using a circuit with small power , which is safer. But in the answer I found the function of the relay is very different from what I know. I attached the question and the answer.

I hope I can find an explanation here.

Thank you all very much in advance.

[PLAIN]http://[url=http://postimg.org/image/pwudznwxd/][ATTACH=full]199660[/ATTACH]
 

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  • #2
phinds
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All I see for your links or images or whatever they are is a broken-link symbol
 
  • #3
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Sorry, it's my first time to upload an image using a host site.


image.jpg

imgurl
 
  • #4
davenn
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Hi there
Welcome to PF :)

since you have told us noting else about the circuit
voltages, lamp type its requirements etc

and you appear to be using TTL or CMOS gates/triggers that means their outputs are VERY limited in the amount of current they can supply
So they will switch a relay which in turn will switch the higher current requires by the lamp

Dave
 
  • #5
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Ok great I understand now. Thank you very much for explaining it to me.
 
  • #6
sophiecentaur
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Relays are also used to switch high voltages (not just high currents), btw.
The Mark Scheme answer is spot on.
 

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