Video Review
Key Concept Summary
TA Summary
Vocabulary
The basic positive charge-carrying particle in an atom.
Metal alloys that are attracted to magnets or are capable of being transformed into a permanent magnet.
A material that does not permit electrons to flow through it.
The matematical formula F = kqQ/d2 which describes the strength of the force between two objects of charge Q and q with their centers separated by the distance d.
A current of electrons that changes direction of flow.
The unit of measure for charge.
Material that allows electrons to flow through it.
The basic negative charge-carrying particle in an atom.
A steady flow of electrons in one direction through a wire.
A repulsive force between electrons near the surface of two different objects.
A number relating the strength of the electric force to the charges involved and their distance apart.
A neutral particle found in the nuclei of atoms.
True/False
Friction comes from electromagnetic forces.
Electric force becomes stronger if the charged objects are moved farther apart.
Neutrons have a negative charge
Iron and nickel are examples of ferromagnetic metals.
Electric currents exert forces on permanent magnets.
Analysis
When a glass rod is rubbed with a rubber sheet, the glass rod becomes positively charged. This is because
Suppose you wanted to exactly double the electric force between two objects. How could you accomplish that?
Free Response
- Describe an experiment that demonstrates that there are two kinds of electric charge.
- Describe the differences between conductors and insulators.
- Describe the important properties of a proton and an electron. What is the comparison in sizes?
- What is electric current?
- How do we know that there is a single electromagnetic force rather than separate electric and magnetic interactions?
- What makes a material ferromagnetic?
- Explain how the contact and friction forces arise and play an important role in the following scenarios:
- A book placed on a table.
- A car tire screeching to a stop at a cross walk to avoid hitting pedestrians.
- A space shuttle reentering Earth’s atmosphere.
- A water skier gliding across the water.
- A rubber rod is rubbed with fur and suspended in the air. A second rubber rod that has been rubbed with fur is placed nearby.
- What charges are on the rubber rods?
- Do the rods attract or repel one another?
- What law explains why this occurs?
- As you bring the rubber rods closer together, what happens to the force between them?
- What could you do to decrease the force between the rods, without changing the distance?
- If you replaced one of the rubber rods with a glass rod that had been rubbed with silk, how would your answers to the above questions change?
Three spheres of metal are placed on stands that act as insulators. Spheres B and Y are neutrally charged. Sphere U holds a strong negative charge. Wire runs between sphere B and Y. Sphere U is brought close to sphere Y.
- Because spheres B and Y hold no net charge, does that mean that no charge exists on them?
- What do we know about the amount of negative and positive charge in spheres B and Y?
- What will sphere U do to the electrons in sphere Y as it approaches?
- What does this do to the net charge on sphere Y?
- What does this do to the net charge on sphere B?
- How is it possible for charge to arise from two neutrally charged objects?
- Describe two ways in which you could turn iron wire into a magnet. Only one of these two methods would work with copper wire. Which one and why?
- If you scuff across wool carpet wearing rubber shoes, you will shock yourself when you reach for a metal doorknob, often before you even touch the knob.
- What type of charge will have accumulated on your body? How do you know?
- When you bring your finger near the doorknob, what happens to the electrons in the metal?
- Explain why, when the metal itself is neutral, a spark will often jump from your finger to the metal before you touch it.