Bellwork (2/4/14) How did you charge the strips in the lab yesterday? How did you charge the strips in the lab yesterday? By friction (rubbing) By friction (rubbing)

Electrostatics 2/4/14

Electrostatics Electrostatics: The study of charges at rest Electrostatics: The study of charges at rest Electricity: any phenomenon associated with electrons (stationary or moving) and other charged particles Electricity: any phenomenon associated with electrons (stationary or moving) and other charged particles

From the textbook define the following in your notes Charge: Charge: Ion: Ion: Electrical Force: Electrical Force: Conservation of Charge: Conservation of Charge: Conductor: (electricity B definition) Conductor: (electricity B definition) Insulator: (electricity B definition) Insulator: (electricity B definition)

Types of particles Electron: a negatively charged “particle” in the atom’s shell or outer layers. (mass is about 1/2000 of a proton and neutron) Electron: a negatively charged “particle” in the atom’s shell or outer layers. (mass is about 1/2000 of a proton and neutron) Proton: a positively charged “particle” in the atom’s nucleus. Proton: a positively charged “particle” in the atom’s nucleus. Neutron: a “particle” with no charge in the atom’s nucleus. Neutron: a “particle” with no charge in the atom’s nucleus.

Structure of the Atom Lithium Example (Atomic Number 3) Lithium Example (Atomic Number 3) 3 Protons 3 Protons 3 Neutrons 3 Neutrons 3 Electrons 3 Electrons 99.97% of the atom’s mass is in the nucleus 99.97% of the atom’s mass is in the nucleus

Electric Charges and Force Electrons are the particles that transfer (do the moving) in atoms and molecules Electrons are the particles that transfer (do the moving) in atoms and molecules Electric charges are conserved Electric charges are conserved Electric force Electric force Like charges repel Like charges repel Opposite charges attract Opposite charges attract

Ions Due to the net transfer (movement) of electrons Due to the net transfer (movement) of electrons If the atom has more electrons than protons it is a negative ion If the atom has more electrons than protons it is a negative ion If the atom has more protons than electrons it is a positive ion If the atom has more protons than electrons it is a positive ion

Example: Carbon Atom Is this carbon atom an ion? Is this carbon atom an ion? 6 Protons 6 Protons 6 Neutrons 6 Neutrons 6 Electrons 6 Electrons It is not an ion It is not an ion Not charged Not charged Red = Proton White = Neutron Blue = Electron

Example: Carbon Atom Is this carbon atom an ion? Is this carbon atom an ion? 6 Protons 6 Protons 6 Neutrons 6 Neutrons 10 Electrons 10 Electrons Yes it is an ion Yes it is an ion Negatively charged Negatively charged Red = Proton White = Neutron Blue = Electron

Example: Carbon Atom Is this carbon atom an ion? Is this carbon atom an ion? 6 Protons 6 Protons 6 Neutrons 6 Neutrons 2 Electrons 2 Electrons Yes it is an ion Yes it is an ion Positively charged Positively charged Red = Proton White = Neutron Blue = Electron

3 Ways to Charge an Object Friction: occurs when electrons are transferred by rubbing Friction: occurs when electrons are transferred by rubbing Contact: occurs when electrons are transferred by direct contact (touching) Contact: occurs when electrons are transferred by direct contact (touching) Induction: occurs in the presence of a charge without physical contact Induction: occurs in the presence of a charge without physical contact

Illustrations on the board Are on the following two slides Are on the following two slides [Lab situations] [Lab situations] [Charging by contact] [Charging by contact]

Triboelectric Series Acetate More Positive Glass Human Hair Wool Aluminum Paper Cotton Wood (Neutral) Hard Rubber Acrylic Polyethylene (Plastic) Rubber Balloon Vinyl Silicone Rubber More Negative Becomes positively charged Becomes negatively charged

Electric Polarization Polarization is a special case of induction Polarization is a special case of induction Where a charged object seems to be attracted to a neutral object Where a charged object seems to be attracted to a neutral object

Balloon and Water Demos - + +

Conductors and Insulators Conductors allow electrons move freely Conductors allow electrons move freely aluminum, silver, gold, iron, copper aluminum, silver, gold, iron, copper Insulators have tightly bound electrons cannot move freely Insulators have tightly bound electrons cannot move freely plastic, wood, dry skin, cotton and wool cloth, rubber, paper plastic, wood, dry skin, cotton and wool cloth, rubber, paper

Grounding Grounding: Allowing charge to move freely to the earth (often making the object neutral) Grounding: Allowing charge to move freely to the earth (often making the object neutral)

Electrostatics Notes and Homework Assignment Read pages and outline in your notes, there will questions about the information on a future Pop Quiz. Answer questions #1-25, in complete sentences, on page to be turned in. (Due on Fri. 2/7/14)

Triboelectric Series electric-series/ electric-series/ electric-series/ electric-series/