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Switches
18 questions By Tony R. Kuphaldt
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Question 10 of 18
What positions do the switches have to be in for the light bulb to receive power?
Reveal answerFor the light bulb to be energized, both switches must either be in the “up” position, or in the “down” position.
Notes:This wiring arrangement (“three-way” switches) is commonly used in residential lighting, for controlling a light bulb in a hallway with switches at either end. Once students relate this circuit to personal experience, it usually makes a lot more sense to them.
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Question 11 of 18
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:
Reveal answer
Notes:DPDT switches are often used as polarity-reversal devices. No doubt your students will see (or build!) this switch arrangement some time in their careers.
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Question 12 of 18
What will the light bulb do when the switch is open, and when the switch is closed?
Reveal answerWhen the switch is closed, the light bulb will receive full voltage from the battery. When the switch is open, the light bulb will receive less voltage (and correspondingly, less current).
Notes:This is another opportunity to review the meanings of “open” and “closed” with regard to switches. Again, students new to electricity often exhibit confusion over these terms, because in the context of doors they hold opposite meanings.
Question 3: but there is a difference! Electricity flows in from positive side, the location impacts the light switch