Charging By Friction When two objects are rubbed together, the molecules are close enough together that the electrons from one substance can move onto the other substance.

The substance that gains extra electrons becomes negatively charged, while the substance with fewer electrons becomes positively charged. The more rubbing, the more transfer, the greater the charge.

The Electrostatic Series As previously discussed, some objects hold their electrons tighter than others. The electrostatic series ranks objects by how easily they let go of e- during friction.

Substances that let go easily are on top and become positively charged. Substances on the bottom hold tight and take on a negative charge. The further the substances are apart, the more charge that it produced.

+ Acetate Glass Wool Fur or hair Silk Aluminium Cotton Paraffin wax Plastic Rubber Gold -

Example When clothes are put in a dryer without fabric softener, they rub against each other and become charged. Which item would take on which charge if:

- + Cotton socks are dried with a wool sweater? - + b) A wool sock is dried with a silk shirt? + -

When you comb your hair with a plastic comb, your hair becomes statically charged.

What is the charge on your hair? + On the comb? -

What could you use to make a comb that would produce less charge? Hair + Aluminium Comb - Acetate

Charging By Contact Electric charge can be transferred between objects just by touching them together. Charging by conduction occurs when a charged object touches a neutral object.

A few electrons move from one object to the other (electrons try to move where they are needed). As a result, both objects end up with the same charge.

Charging By Introduction Neutral objects are attracted to charged objects. In fact, a charged object can induce a charge in another object.

The neutral object never actually gains or loses any electrons. When the charged object is brought close, the electrons move slightly in the uncharged object.

So if a positive object in brought near, the electrons are attracted and move closer. If the charge is negative, the electrons are repelled and move away.

Discharging An Object If you connect an electrical device or something with a charge to the earth or the ground, then the extra charges get transferred into the Earth. Since the Earth is so large, it can accept a lot of electrons without having much effect. This is called grounding an object.