In a circuit, the switch
A) opens and closes the circuit
B) starts and stops the electrons

What happens when the switch in an electronic circuit is closed and opened?
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2 Answers
Profile photo for William Rose
William Rose
, Electrical Engineer, Mechanic
Answered 1 year ago · Author has 479 answers and 2.2M answer views
Assuming you do mean electronic and not electrical circuits, then the answer is, most of the failures. Powering up and down electronics stresses most components more than leaving them running all the time. First there is temperature stresses as a cold component begins to warm up. Then there are the voltage and current spikes and surges created as capacitors charge up, inductors build their fields, etc. And its not just the components but the stray capacitance and inductance as well.

Basically, when you turn on a device and it doesn’t work, chances are it failed the moment you turned it on (or the moment you last turned it off). They rarely fail while they are running. An old adage in electronics is, the longer a device operates, the longer it will operate.

I always plug in my power supplies for my phone, laptop, etc., before plugging it into the device so the power supply can stabilize without a load on it. Then I plug it into the device. Then I turn on the device. The idea is to minimize the spikes and surges.

BTW, its the same with incandescent light bulbs. A cold filament is rapidly heated which is a thermal stress. Then there is a mechanical stress caused by the current rushing through the coiled filament which creates a mechanical torque on the filament. That’s why you usually (not always) see a bulb fail when you first switch it on

Adozen is 1221/12 = 1.751.75 x 12 = 21therefore, 1.75 is the answer.