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Moving Can. The Challenge: Use the plastic tube and sheet of plastic to move the can without physically touching it. Electrostatics. Chapter 32. Forces. There are four basic kinds of forces: 1) Gravitational 2) Electromagnetic 3) Strong Force 4) Weak Nuclear Force. Forces.
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Moving Can The Challenge: Use the plastic tube and sheet of plastic to move the can without physically touching it.
Electrostatics Chapter 32
Forces There are four basic kinds of forces: 1) Gravitational 2) Electromagnetic 3) Strong Force 4) Weak Nuclear Force
Forces Gravitational forces: - we’ve discussed already this year - is dependent on the masses of the two objects - we feel the effect of it as weight
Forces Electromagnetic forces: - think about magnets; what do you already know? - like ends repel - opposites attract - it’s the same with positive and negative charges!
Forces The Strong Force: What’s wrong with this picture?
Forces The Strong Force: Scientists theorized that since the nucleus of an atom contains only positive charges, there must be some kind of force that only applies to very small particles over very small distances to keep them from repelling each other. So they said, “Let’s call it the strong force.”
Forces Weak Nuclear Force: - pertains to nuclear decay and we will discuss this one at more length later in the year.
Forces So let’s put them in order from strongest to weakest: 1) Strong force 2) Weak nuclear force 3) Electromagnetic forces 4) Gravitational force
Charges • An atom consists of charged particles protons = positive; electrons = negative • Objects become charged by the addition or removal of electrons • Ion = a charged atom
Conservation of Charge Charge is not created out of thin air. If an object becomes positively charged, it is usually because another becomes negatively charged. This is conservation of charge.
Charges Charged objects attract or repel each other with electrical forces
Charges Like charges repel.
Charges Opposite charges attract.
Coulomb’s Law French physicist Charles Coulomb Developed the equation for calculating electrical force between charges Coulomb’s constant: k = 9 X 109 Nm2/C2
Object A has a positive charge of 9.0 X 10-6 C. Object B, having a positive charge of 4.5 X 10-6 C, is 0.030 m away. Calculate the force on A. What is the force on B?
Electric Field Lines From yesterday’s activity, we could tell that force vectors around a charge look something like this:
Electric Field Lines This is what the electric field lines look like around positive and negative charges:
Electric Field Lines This is how the field lines interact for two opposite charges positioned near each other:
Electric Field Lines What would it look like for two similar charges positioned near each other?
Electric Field Lines What would it look like if to flat plates were place near each other, one positively charged, the other negatively?
Conductors Electrons are free to move within conductors. Metals are good conductors.
Insulators Materials that have electrons tightly bound to their atoms. They are less likely to move around. Glass and rubber are good insulators
Methods of Charging Friction * most common * electrons are being transferred from one material to another * like scooting your feet on the carpet
Methods of Charging Contact * electrons can be transferred from one material to another * when a charged object comes in contact with a neutral object
Methods of Charging Induction * using a charged object to create a charge in two others by separation
Methods of Charging Induction with Grounding * using a charged object to cause a separation of charges in a neutral object and then either removing or adding electrons by putting in contact with the ground
Methods of Charging The bottom of a negatively charged cloud induces a positive charge at the surface of the ground below. This leads to lightning so the cloud discharges.
