Unit 5 Physics Test

B, C, and D

A metal sphere is electrically neutral. It is touched by a positively-charged metal rod. As a result, the metal sphere becomes charged positively. Which of the following occur during the process? Select all that apply. A. The metal sphere gains some protons. B. Electrons are transferred from the sphere to the rod. C. The metal sphere loses electrons. D. The overall charge of the system is conserved. E. Protons are transferred from the rod to the sphere. F. Positive electrons are moved between the two objects.

1. The electron would move to the RIGHT, since electrons move from low to high potential 2. There would be an electron on the LEFT-HAND SIDE electric field, and there would be a PROTON on the RIGHT-HAND SIDE electric field. High potential would be found around a positive charge, and low potential around a negative charge 3. The proton would move to the LEFT, since a proton would instead move from high to low potential

Consider the diagram below, which shows the electric potential due to some charges (not shown) and a single electron (in blue) placed into this electric field. 1. Draw an arrow to indicate the direction the electron will move. (Hint: it will move horizontally.) 2. Draw any charged objects (including the sign of the charge) that you think must be present in order to generate the electric potentials you can see in the diagram. 3. If the electron were instead swapped out for a proton, in which direction would the proton move?

No, since they have no charge and since they don't generate an electric field

Do neutrons exert electrical forces on other particles? Why or why not?

C

During a physics lab, a plastic strip was rubbed with cotton and became positively charged. The correct explanation for why the plastic strip becomes positively charged is that: A. the plastic strip acquired extra protons from the cotton. B. protons were created as the result of the charging process. C. the plastic strip lost electrons to the cotton during the charging process.

attractive

Electric forces can be attractive or repulsive, but gravitational forces are always ________.

quarter (divide by four)

If you double the distance between two charged objects, the electric force will ______.

quarter (divide by four)

If you double the distance between two objects with mass, the gravitational force will _____.

Sphere A is rubber, because it is an insulator (which does not allow the charges to move around and spread out). Sphere B is copper, because it is a conductor (which allows charges to move easily and spread out).

One of these isolated charged spheres is copper and the other is rubber. The diagram below depicts the distribution of negative charge over the surface of two spheres. Label which is which and support your answer with an explanation.

False, since it contains equal numbers of protons and electrons.

True or False An object which is electrically neutral contains only neutrons.

True

True or False The strength of an electric field around a single positive source charge gets weaker as you move away from it.

True

True or False You exert the same gravitational force on the Earth that the Earth exerts upon you.

False, since it must loose electrons.

True or False For a neutral object to become positively charged, it must gain protons.

D

Upon entering the room, you observe two balloons suspended from the ceiling. You notice that instead of hanging straight down vertically, the balloons seems to be repelling each other. You can conclusively say: A. both balloons have a negative charge. B. both balloons have a positive charge. C. one balloon is charged positively and the other negatively. D. both balloons are charged with the same type of charge.

mass; charge

What does gravitational force vary linearly with? What does electric force vary linearly with?

The electric potential energy decreases, since the lost potential energy is transformed into heat, light, kinetic energy, etc.

What happens to the electric potential energy of a charge as it moves from a position of higher electric potential to a position of lower electric potential?

voltage

What is electric potential or potential difference also sometimes called?

Electric potential energy is the total energy stored in a charge due to its position in an electric field. Therefore, at a given location, a larger charge will have more electric potential energy than a smaller charge at that same position). Electric potential is a ratio of the electrical potential energy that a charge will have at a given location per its amount of charge. Therefore, at a given location, a larger charge and a smaller charge will both be at the same potential. Since a larger charge will also have more electric potential energy stored in it, the ratio of its energy per charge will be the same as the ratio for the smaller charge.

What is the difference between electric potential energy and electric potential?