few general formulas

[nix85]

another random fact

[nix85]

another random fact

Miniature Circuit Breaker (MCB) is used for overcurrent and short circuit
protection. it is using electromagnet to break contact for short circuit
and slower, heating bending element made of two different metals
(say copper and steel) to slowly break contact on prolonged overcurrent.
it does not protect people from shock cause it needs big current to activate
while man can die from as little as few dozen miliamps.

for this is used RCD aka FID. it uses a small toroid core with phase and neutral
windings perfectly canceling each other's magnetic field. in a case of slightest
current difference between the two (as in case when grounded man touches live
and some current flows through him back to neutral) magnetic field is produced
and picked up by third winding which instantly trips the switch and man is saved.

https://www.youtube.com/watch?v=oYLIpN4RwEg
https://www.youtube.com/watch?v=Q_bceXFTYnI

[perpetual]

Another correction: momentum = mv.

Of course it is.

These formulas are on my blog too now

https://vril12.wordpress.com/few-general-formulas/

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