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Homework Help: Normally open switch & Normally closed switch.

  1. Apr 11, 2013 #1
    This is not really a homework question. Just a question regarding the normally open (NO) and normally closed switches.

    For an NO switch, if the button is pressed (not open anymore) and then the button is released, is the switch still in the "not open" state or does it go back to the open state?
  2. jcsd
  3. Apr 11, 2013 #2


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    Staff: Mentor

    Usually a Normally Open switch has contacts that connect only as long as the switch is operated (think of a doorbell button being pressed to ring a buzzer; spring action breaks the contact as soon as finger pressure is released).
  4. Apr 12, 2013 #3


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    I don't believe "an NO switch" is a sufficient description to answer the question.

    I'd say it depends if the push button switch is a "latching" or "non-latching/momentary" type...

    Non-Latching/momentary: Switch is closed only while the button is pressed. So when you release it the switch returns to the open condition.

    Latching: Switch is open when the button is in the "out" position. When pressed the button moves to the "in" position and the switch is closed. When released the button stays depressed and the switch stays closed. When pressed again the button comes out and the switch opens.

    The above describes a NO type but either can be NC or both (eg they have both NO and NC terminals).
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