Chapter 20Electricity

Section 1Electric Charge and Static Electricity

A. Electric Charge1. The charged parts of the atom are the protons and electrons.2. Protons have a positive charge (+), electrons

have a negative charge (-) 3. If two charges are the same, they will repel

each other. If the charges are opposite, they will attract.

4. Magnets work the same way.

B. Electric Force

1. Electric force is the attraction or repulsion between electric charges.

2. Electric Field – the area around a charged object where the objects electric force is exerted on other charged objects.

a. Fields are invisibleb. Shown using arrows which indicate the

direction of the electric force. c. Fields get weaker as distance increases.

Draw This Electric field around a single charge.

Positive Charge Negative charge

Electric fields around multiple charges

C. Static Electricity1. Normally, most objects have no overall

charge (same numbers of positives and negatives).

2. Protons are bound to the center of the atom but electrons can get removed.

3. If an object loses electrons it becomes +4. If an object gains electrons it becomes –5. The build up of charges is called static

electricity. Static means “not moving.”

D. Transferring Charge

1. Charges are neither created or destroyed (Law of conservation of charge).

2. There are three ways to transfer a charge.a. Friction

The transfer of electrons from one object to another by rubbing. Ex. socks on carpet.

b. Conduction When a charged object touches another object. Ex. Your feet are touching the

socks as they get charged and your body gets charged.

c. Induction Charging when there is no touching but the

field of one object moves electrons in another object. Ex. lightning clouds.

3. Charges can be detected using induction with an electroscope.

Not touching

E. Static Discharge

1. When a negatively charged objects are brought together, electrons move transfer until both objects have the same charge.

2. Often produces a spark. The spark is heated air. Ex. Lightning