Why spark will occur when you switch on any device?

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smslca

Registered Senior Member
When you switch on any electrical appliance you will observe some spark in the switch. Do you why spark will occur?
Here is the answer…..
Air’s dielectric strength is 20Kv/cm. That means when you apply 20Kv voltage between two terminals and the distance between those terminals is 1 cm then dielectric strength of air will be broken between these two terminals and air will behave like conductor. Then you can observe the spark there. In normal house applications the voltage commonly used is 230V. So if the gap between terminals is 0.01cm then in that gap air will conduct for 230V voltage. At that time spark will occur.

Please let me know if there are any mistakes in this article.... :D
 
Well, it is not exactly incorrect, but... The dielectric strenght of air varies considerably with temperature and moisture, and is more likely to be about 10kv/cm.

So, as the contacts come near to each other, there will be a spark. Note that 230VAC will peak at 325V. However, the main reason for sparks when turning on appliances is usually something else: Even a quality switch will not be bounce-free. In other words, it will not just switch on, it will switch on and off a number of times, before staying on. Combined with inductive loads or high turn-on currents, this is the main creator of sparks.

Hans
 
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