Physics 1201 Chapter 16 Conceptual

As an object acquires a positive charge, its mass usually a) decreases b) increases c) stays the same d) becomes negative

a) decreases. If an object acquires a positive charge, it loses e⁻, and vice versa. It lost e⁻, therefore the mass decreased.

Q₁ = - 10 C is located at the origin. Q₂ = .10 C is located on the positive x axis at x = 1.0 m. Which of the following is true of the force on Q₁ due to Q₂? a) it is attractive and directed in the +x direction. b) it is attractive and directed in the -x direction. c) it is repulsive and directed in the +x direction. d) it is repulsive and directed in the -x direction.

a) it is attractive and directed in the +x direction

Refer to the picture. If two charged plates were moved until they are half the distance shown without changing the charge on the plates, the electric field near the center of the plates would a) remain almost exactly the same b) increased by a factor of 2 c) increase, but not by a factor of 2 d) decrease by a factor of 2 e) decrease, but not by a factor of 2

a) remain almost the same

To be safe during a lightning storm, it is best to be a) in the middle of a grassy meadow b) inside a metal car c) next to a tall tree in a forest d) inside a wooden building e) on a metal observation tower

b) inside a metal car. This is due to shielding

We wish to determine the electric field at a point near a positively charged metal sphere (a good conductor). We do so by bringing a small positive test charge, q₀ to this point and measure the force F₀ on it. F₀/q₀ will be ____________ the electric field as it was at that point before the test charge was present. a) greater than b) less than c) equal to

c) equal to. The test charge's charge does not matter, because it cancels out of the equation.

Which vector best represents the direction of the electric field at the fourth corner of the square due to the three charges shown in the figure

D

The picture shows electric field lines due to a point charge. What can you say about the field at point 1 compared with the field at point 2? (The picture shows that point 1 is closer to the charge than point 2) a) The field at point 2 is larger, because point 2 is on a field line. b) The field at point 1 is larger, because point 1 is not on a field line. c) The field at point 2 is zero, because point 1 is not on a field line. d) The field at point 1 is larger, because the field lines are closer together in that region.

D. Electric field (E) = F/q. F/q = ((KQq)/r²) / q. E = (KQ)/r². *The charge of the points don't matter, because they cancel, but the distance does.*

Fred the lightning bug has a mass m and a charge + q. Jane, his lightning-bug wife, has a mass of 3/4 m and a charge -2q. Because they have charges of opposite sign, they are attracted to each other. Which is attracted more to the other, and by how much.

They are attracted to each other the same amount (F = (KQq)/r². Mass is irrelevant)

A negative point charge is in an electric field created by a positive point charge. Which of the following is true? a) The field points toward the positive charge, and the force on the negative charge is in the same direction as the field. b) The field points toward the positive charge, and the force on the negative charge is in the opposite direction as the field. c) The field points away from the positive charge, and the force on the negative charge is in the same direction as the field. d) The field points away from the positive charge, and the force on the negative charge is in the opposite direction as the field.

d) The field points away from the positive charge, and the force on the negative charge is in the opposite direction as the field. Electric field lines always point away from positive charges (and toward negative charges). And the force on the negative charge is toward the positive charge, and therefore in the opposite direction of the field.

We are usually not aware of the electric force acting between two everyday object because a) the electric force is one of the weakest forces in nature b) the electric force is due to microscopic-sized partiles such as electrons and protons c) the electric force is invisible d) most everyday objects have as many plus charges and minus charges

d) most everyday objects have as many plus charges and minus charges

A small metal ball hangs from the ceiling by an insulating thread. The ball is attracted to a positively charged rod held near the ball. The charge of the ball must be a) positive b) negative c) neutral d) positive or neutral e) negative or neutral

e) negative or neutral. It has to just be less positive than the ball.