# Static Electricity Notes

Revision notes on static electricity for p2.

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STATICELECTRICITY
STATIC ELECTRICITY IS CAUSED WHEN CHARGES ARE NOT FREE TO MOVE AND THEY BUILD
UP IN ONE PLACE. WHEN THE DO MOVE IT CAUSES A SPARK OR SHOCK.
1) Build-up of static is caused by friction.
When two insulating materials rub together, electrons can be rubbed off one and
on to another.
This will leave a positive static charge on one and a negative charge on the other.
The direction of the transfer depends on the two materials.
Electrically charged objects attract small objects ­ a charged balloon could make
small pieces of paper `dance'.
2) Only the electrons move.
Both positive and negative charges are cause by the movement of electrons.
If an object receives electrons it is negatively charged and if it loses electrons it is
positively charged.
A charged conductor can be grounded with a metal strap. The electrons will flow
down to earth if the charge is negative and up to the object if its charge is positive.
The rate of this flow is the current.
3) Opposites attract.
If there are two negative charges are near each other, they will repel. And if a
positive and negative charge is near each other, they will attract.
The further apart the charges, the weaker this force.
4) As charge increases, so does voltage.
The greater the charge on an object, the greater the potential difference between
it and Earth.
If the voltage is too high, it will create a spark which jumps across the gap. High
voltage cables can be dangerous when sparks jump from them to Earth ­ this has
been known to happen, but not often.
When hair sticks up it's because the electrons are repelling each other.

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