Spark from immersion heater switch

[Harry Bloomfield]

The spark size and strength is caused by the energy present. Bigger or smaller switch doesn't change the energy present. No matter how fast you flick the switch, the arc operates at the speed of light. As soon as the switch breaks contact, the arc charge begins.

The faster and wider the gap becomes, the shorter the period of arcing. The arc persistance is also effected by the point in the voltage sine wave when the switch is operated and what type of load is being switched. Inductive and capacitive loads being the most difficult to switch, resistive ones the easier ones.

 

[DiyNutJob]

There are no such regulations preventing the installation of a more robust than strictly necessary switch. The action of the switch will be brisker, the contacts more capable, therefore the resultant arc will be shorter and less obvious. Arc duration is a function of the speed with which contact is broken, which is why higher current and voltage switches, use a wind up and press a mechanical button to trigger make or break and/or oil submersion and/or an insulated barrier dropping into the gap to break the arc.

It depends if you accept the arc travels at the speed of light. If you agree to that then you can't outrun it.

 

[Harry Bloomfield]

It depends if you accept the arc travels at the speed of light. If you agree to that then you can't outrun it.

An arc is limited by distance. The faster distance is achieved, the shorter the arc, but the arc is broken 100 times per second anyway, on ac mains - which neatly explains why dc is so much more problematic to switch.

 

[RandomGrinch]

It depends if you accept the arc travels at the speed of light. If you agree to that then you can't outrun it.

So these arcs are 'travelling' at the speed of light?

 

[RandomGrinch]

...and if you don't believe us, maybe you might have more trust in Wikipedia!

https://en.m.wikipedia.org/wiki/Arc_flash

 

[DiyNutJob]

An arc is limited by distance. The faster distance is achieved, the shorter the arc, but the arc is broken 100 times per second anyway, on ac mains - which neatly explains why dc is so much more problematic to switch.

Not sure why you think the arc is broken 100 times a second. Lightning is an arc. It's a single strike dissipating most of the accumulated energy.

 

[JohnD]

Not sure why you think the arc is broken 100 times a second.

Because it's AC.

 

[Harry Bloomfield]

Not sure why you think the arc is broken 100 times a second. Lightning is an arc. It's a single strike dissipating most of the accumulated energy.

Do you not understand how an ac voltage works?

100 times per second, the voltage drops to zero volts, although there will be ionised metal from the contacts, in the gap, which might help sustain the arc beyond the zero crossing point.

Lightning is a dc voltage, releasing a stored electrostatic charge of millions of volts, over a very brief period. It does not though, travel at the speed of light. The actual discharge normally progresses from the earth, up to the charged cloud.

 

[BS3036]

Thank god we have the internet to teach us all basic physics!