Switches

Basic Electricity

  • Question 1

    What is the purpose of the switch shown in this schematic diagram?



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  • Question 2

    How is an electrical switch constructed? What goes on inside the switch that actually “makes” or “breaks” a path for electric current?

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  • Question 3

    What difference will it make if the switch is located in either of these two alternate locations in the circuit?





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  • Question 4

    Does this switch (in the closed state) have a low resistance or a high resistance between its terminals?



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  • Question 5

    How might you use a meter (or a conductivity/continuity tester) to determine whether this electrical switch is in the open or closed state?



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  • Question 6

    Identify the following types of switches, according to the number of “poles” and “throws” each switch has:



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  • Question 7

    Identify the following types of switches, according to their style of actuation (how each switch is physically operated):



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  • Question 8

    What type of switch is represented by this schematic symbol?



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  • Question 9

    What type of switch is represented by this schematic symbol?



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  • Question 10

    What positions do the switches have to be in for the light bulb to receive power?



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  • Question 11

    Electric motors of the permanent magnet design are very simple to reverse: just switch the polarity of the DC power to the motor, and it will spin the other direction:



    Complete this schematic diagram, showing how a DPDT switch may be placed in this circuit to reverse the motor’s direction of rotation without the need to disconnect and re-connect wires:



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  • Question 12

    What will the light bulb do when the switch is open, and when the switch is closed?



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  • Question 13

    Examine this schematic diagram:



    Now, without moving the following components, show how they may be connected together with wires to form the same circuit depicted in the schematic diagram above:



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  • Question 14

    What does the normal status of an electrical switch refer to? Specifically, what is the difference between a normally-open switch and a normally-closed switch?

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  • Question 15

    Identify the “normal” status of each switch, whether it is normally-open (N.O.) or normally-closed (N.C.):



    Based on the symbols shown, describe what physical condition results in the switch contacts being open, and what condition results in the switch contacts being closed, for each switch.

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  • Question 16

    Identify the “normal” status of each switch, whether it is normally-open (N.O.) or normally-closed (N.C.):



    Based on the symbols shown, describe what physical condition results in the switch contacts being open, and what condition results in the switch contacts being closed, for each switch.

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  • Question 17

    Identify the “normal” status of each switch, whether it is normally-open (N.O.) or normally-closed (N.C.):



    Based on the symbols shown, describe what physical condition results in the switch contacts being open, and what condition results in the switch contacts being closed, for each switch.

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  • Question 18

    Find one or two real switches and bring them with you to class for discussion. Identify as much information as you can about your switches prior to discussion:

    • Number of poles
    • Number of throws
    • Voltage rating of contacts
    • Current rating of contacts
    • Contact status for various actuator positions
    • Type (toggle, pushbutton)
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