Switch spark suppression

Wanting to know if the contacts in switch s1 spark (see circuit diagram), I did a simple test and found that there are no sparks even with high amperage.

Is there anyone that could explain why this is so? Also, would it make a difference if the switch were to toggle at frequency as there will be rapid current reversal in wire 1, notwithstanding that I appreciate the fact that there is not inductive load?

Thank you.

by Drig
November 04, 2018

In your circuit as drawn there is never any current in the switch contacts. The current in wire 1 is always zero. There will never be any sparking.

by mikerogerswsm
November 04, 2018

Hi Mike, Thank you for your quick answer. I appreciate that wire w1 sees no potential difference between its ends. I am intrigued, however, by the fact that as I vary the effective conductor area either side of sw1, (therefore changing the resistance somewhat) there is no current flow in w1. I have difficulty in grasping things in a visual analogue.

by Drig
November 04, 2018

I think this is what you have in your mind:


At high currents it will spark and the solution is to put 0.1uF across the switch contacts.

by mikerogerswsm
November 04, 2018

The spark is more dependent on voltage (or current and inductance), so there won't be much sparking below 100V.

by mikerogerswsm
November 05, 2018

Hi Mike, The circuit https://www.circuitlab.com/circuit/pw6e8g8e393v/20-switch/ is clear. I specifically refer to the circuit I presented. It is not clear to me what exactly happens with the current in wire w1 (and other wires for that matter) as the switch is operated.

by Drig
November 05, 2018

The circuit you presented has no voltage applied to the switch. The contacts are shorted together. There is no emf to cause current to flow in wire w1. Remove the battery and resistor, they don't do anything. It is just a switch and a couple of wires.

by mikerogerswsm
November 05, 2018

Hi Mike, Thank you very much for all your effort and I apologize for being a nuisance. Best regards, Dragan

by Drig
November 05, 2018

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