# Physics II

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Static electricity

Static electricity is where two insulating materials are rubbed together and the friciton causes electrons to be knocked off of one matrail and onto another. As the materials are insulators they do not allow this charge to flow through them and instead they hold onto or store the charge allowing it to build up - this build up is called static electricity. Charged objects can attract small uncharged bits of paper.

Like charges repel

Opposite charges attract

Discharge

A charged conductor can be discharged by connecting it to the earth with a metal strap. If the object was nnegatively charged then electrons will flow down the stap and to the ground. If the object was positively charged then electrons will flow up the wire and to the object. If however there is a large potential difference this can cause a spark to jump across the gap between the charged object and conductor which can be dangerous for e.g. petrol stations.

Neutral objects

Charge objects can attract uncharged objects. For example if a negatively charged rod is hovered over uncharged paper they attract as the negative charges on the rod repel the negative charges on the paper to the other side of the paper leaving the positive chages on the surface. As positive and negative charges are opposite they attract. If the rod was positively charged then it would simpley attract the negative charges towards it.

Electroscope

As you hover a negatively charged rod over the electoscope cap, the negative charges from the rod repel the same negative charges down the electroscope which  causes the gold foil to become negatively charged. As like charges repel this causes the negative rod an d foil to repel which causes the leaf to rise.

Lightining

Inside a storn cloud rain droplets and ice particles are bumping around which causes electrons to be rubbed off of one material…