190 likes | 728 Views
Electrostatics. Electrical Force and Charges. Electrical forces come from charged particles in atom Charge is a property of attraction or repulsion 2 kinds positive (+) charge (protons) negative (-) charge (electrons). Facts about atoms.
E N D
Electrical Force and Charges • Electrical forces come from charged particles in atom • Charge is a property of attraction or repulsion • 2 kinds • positive (+) charge (protons) • negative (-) charge (electrons)
Facts about atoms. • every atom has a positively charged nucleus surround by a negatively charged electrons • all electrons are identical • The nucleus is made of protons and neutrons. All protons are identical and neutrons are identical. Neutrons are neutral (no charge). • Atom are neutral that is the number of protons is equal to the number of electrons
objects become charged by gaining or losing electrons (- charge) when objects lose electrons they become positively charged when objects gain electrons they become negatively charged
The Electromagnet Force depends on the charge of the particles and on the distance between them. • objects with the same charge repel each other………LIKES REPEL • objects with opposite charges attract each other…….OPPOSITES ATTRACT
Conservation of Charge • An object that has an unequal number of protons and electrons is charged. • electrons are free to move • Conservation of charge - electrons are not created or destroyed but are simply transferred from one substance to another.
Coulomb’s Law • The electric force between two charged particles is directly proportional to the charge and inversely proportional to the square of the distance between the charges. kC is Coulomb’s constant kC = 8.99 x 109 N x m2/kg2
The unit for charge is the Coulomb (C) • it takes 6.2 x 1018 electrons/protons to make up the charge of one coulomb • the charge on 1 electron is -1.60 x 10-19 C • the charge on 1 proton is 1.60 x 10-19C
Conductors and Insulators • Conductors are materials that allow the flow of electricity. • example metals – the electrons are loose and able to move • Insulators are materials that resist the flow of electricity. • example rubber or plastic – the electrons are held tight and can not move freely. • Semiconductor are materials that can be made to behave as a conductor or insulator • example silicon
1. What are the two types of electric charge? • 2. True or false? In an atom, negatively charged electrons surround a positively charged nucleus. • 3. True or false? If a neutral atom gains one or more electrons, it becomes a positively charged ion. • 4. Circle the letter of each sentence that is true about electric force. • Like charges attract and opposite charges repel. • Electric force is the attraction or repulsion between electrically charged objects. • Electric force is inversely proportional to the amount of charge. • Electric force is inversely proportional to the square of the distance between two charges. • 5. Which are stronger inside an atom, electric forces or gravitational forces? • 6. True or false? Electric forces cause friction and other contact forces. • 7. What is Coulomb’s Law? • 8. What does the electrical force depend on?
Charging by Friction and Contact • Charging by friction happens when materials are rubbed together. • examples • rubbing a balloon in your hair • walking across carpet • Charging by contact is when electrons are move from a charged object to an uncharged object when they touch • examples • when I touched the charged rod to the pith ball.
Charging by induction • If a charged object is brought near a surface without touching the electrons will move leaving the surface charged. • grounding is when we allow charges to leave
Charge Polarization • when one side of an atom becomes slightly more positive or negative than the other.