Explain why the metal strips on an electroscope move apart when an electrically charged wand is brought near the metal sphere.

Is it correct to say the positve charges are pulled up to the metal sphere, and the negative charges are pushed down to the metal strips?

Does an induced dipole (like the electroscope above) have a net negative charge, net positive charge, or is it electrically neutral? Explain.

In the electroscope example below, are there protons (positive charges) in the leaves? Explain why or why not:

2. Like charges       , and opposite charges       .

Rubbing a balloon on your head and sticking it to a wall is a good example of the two facts stated above. Explain what is happening when:

Rub the balloon on your hair:

Bring the balloon near the wall:

Touch the balloon to the wall:

HOw is this similar to the electroscope demonstration?

3. Explain how a Van De Graff generator works.

In the picture below, the person is standing on plastic (an insulating material). Draw in how the charges are distributed from the generator to the person, and explain why the person's hair sticks up and out from the body.

Explain what happens when another person comes close to the person on the chair?

Explain why you would still get shocked if you jumped in the air and touched the generator even though you aren't grounded.

What would have to be true in order for you to jump in the air and not get shocked if you touched the generator.

4. List the following sub-atomic particles in order from largest to smallest mass: proton, neutron, and electron.

Does mass have anything to do with electric charge? Prove your answer.

For Honors Physics. Basic physics can skip down to the last question:

Using the information on the back of your lecture sheet, calculate how much larger a proton is compared to an electron. (1836 times more massive)

Consider the following diameters:

P = 1(10^-15) meters

e = 1(10^-18) meters

Distance from electron to nucleus of a hydrogen atom = 5.3(10^-11) meters

If you wanted to scale up the size of a proton to about the size of a basketball (.25 meters = 10 inches) you would have to multiply the diameter of the proton by a scaling factor of 2.5(10^14). Scale up the diameter of the electron and distance between electron and proton.

Electron: (.00025 meters = 1/10 of an inch)

Distance: (13,250 meters = 8 miles)

This means if you the nucleus of a hydrogen atom was the size of a basketball, the electron would be roughly the size of your pinky and would have to be placed 8 miles from the basketball! What can you conclude about the makeup of an atom? In other words, what makes up most of an atom?

5. What relationship does electric force have with the distance between the charges?

How does that compare with Gravity?

If the electric force between two certain particles is .003 N when they are .05 meters apart, what is the force between them if the distance is increased to .10 meters? (.00075 N) Show how you get this answer!

What would the electric force be if the distance was decreased to .0125 meters? (.048 N) Show how you get this answer!

6. What relationship does electric force have with the product of charges?

If the electric force between a 3.2(10^-19) C charge and a 1.6(10^-19) C charge is .010 N at a certain distance, what is the force if the first charge weakens to 1.6(10^-19) C? (.005 m) Show how you get this answer!

What would be the force if the first charge was restored to its original value, and the second charge strengthened to 4.8(10^-19) c? (.030 N) Show how you get this answer!

7. A charge of -5.0(10^-7) C is 10 cm from a charge of +6.0(10^-6) C. Find the magnitude and direction of the force on the -5.0 charge. (F = + 2.7 N, which is towards the +6.0 charge)

What is the magnitude and direction of the force on the +6.0 charge? Explain why. (F = -2.7 N, which is towards the -5.0 charge)

A charge of +5.0(10^-9) C is attracted by a charge of -3.0(10^-7) C with a force of .135 N. How far apart they? (x = 10 mm = .01 m)

For Honors Physics Only:

A particle carrying a charge of +6.0(10^-7) C is located halfway between two other charges, one of +1.0(10^-6) C and the other of -1.0(10^-6)C, that are 40 cm apart. All three charges lie on the same straight line. What is the magnitude and direction of the force on the +6.0 charge? (F = .27 N toward the negative charge)

8. Explain each of the four forces in the Universe.

Gravity:

Electro-Magnetic:

Weak Nuclear:

Strong Nuclear:

If the Electric force is so much stronger than gravity, why doesn't it dominate our everyday life?

List the four fundamental forces in the Universe in order from weakest to strongest.

1.

2.

3.

4.

From the following values of forces for two certain particles:

Gravity: F = 5.0 (10^-44) N

Electro-Magnetic: F = .00005 N

Weak Nuclear: F = 5.0 (10^-8) N

Strong Nuclear: F = .005 N

determine how much larger the Strong Nuclear is compared to the Electric-Magnetic force. Show how you get this answer!

How much larger is the strong nuclear compared to the Weak Nuclear? Show how you get this answer!

How much larger is the strong nuclear compared to gravity? Show how you get this answer!

9. Give the two rules of electric field lines:

1.

2.

Given the picture below of one electron and its electric field, which point (a or b) is located at a stronger place in the field?

You learned that the Van de Graff generator uses a rubber belt to produce a net electric charge on the metal sphere. Does all of the negative charge reside on the outside surface of the sphere? Explain.

Given the two charges below with their electric field lines, how do you know that the two particles have the same charge?

What happens to the electric field lines when one of the charges is stronger than the other?

Given the table below, fill in the appropriate equations.

10. Four protons are located .001 meters from nine more protons. Find the point between them where the electric field strength is exactly zero. (.0004 meters from the four protons.)

If an electron was placed at that exact point, why wouldn't it move?

For Honors Physics Only:

A charge of + .0064 C is located .0006 meters from another charge of + .0144 C. Find the point between them were the electric field is zero. (.00024 meters from the .0064 charge).

Show algebraicly that the distance, x, where the electric field is zero is given by the following equation:

11. It takes a certain amount of work to move an electron across two charged plates (moving it from the positive plate to the negative plate). How much more work would it take to move it if the distance between the plates were doubled?

How much would it take if the distance was reduced by a third?

What is the relationship between the work done on a charge and the distance between plates?

(New Question)It takes a certain amount of work to move an electron across two charged plates. How much more work would it take to move it if the electric field strength between the plates was quadrupled?

How much would it take if the electric field strength was reduced by half?

How do you increase the electric field strength?

What is the relationship between the work done on a charge and the electric field strength between plates?

(New Question) It takes a certain amount of work to move an electron across two charged plates. How much more work would it take if the distance was doubled, and the electric field strength were tripled?

Based on these questions, explain in words how you can increase or decrease the amount of work done on a charge between two elecrically charged plates.

How does the amount of work done on the charge relate to the potential difference between the plates? Explain using concepts from last semester.

How does the potential between two charged plates relate to the charge's energy?

12. Explain what the potential difference is between two terminals of a battery in terms of the amount of work to move an electron.

What does a low potential (low voltage) mean for a battery?

Does a low potential (low voltage) mean when the electron is allowed to move from the negative terminal to the positive terminal it has a low energy or high energy?

How does that energy of the electron relate to the brightness of a light bulb?

If you want the light bulb to be brighter, do you need a high potential or a low potential?

13. Explain two scenarios you can be safe while touching a wire with a high potential.

Explain why it is safe to be touching 5,000 Volts with both hands as long as your feet are not touching the ground.

Identify the two things necessary to have a ciruit:

a.

b.

Explain what current is.

Explain how a big current would translate to the work on the electron, and the potential between the two terminals.

Explain what resistance is in a circuit.

What is the role of resistance in a circuit?

Does resistance increase or decrease the energy of an electron?