MIDTERM 1 multiple choice questions from Homework(WEBASSIGNand Quizes)

A flat surface having an area of 2.05 m2 is placed in various orientations in a uniform electric field of magnitude E = 4.05 ✕ 105 N/C. THIS IS IMPORTANT-- C! (a) Calculate the electric flux through this area when the electric field is perpendicular to the surface. (b) Calculate the electric flux through this area when the electric field is parallel to the surface. (c) Calculate the electric flux through this area when the electric field makes an angle of 64.0° with the plane of the surface.

(A) 2.05*E=answer (B) 2.05*E*cos(90)=0 (C) *IT IS NOT 2.05xEcos(64)=answer* IT IS 2.05xEcos(90-64)=answer IT IS 2.05xEcos(26)=answer

If more electric field lines are leaving a gaussian surface than entering, what can you conclude about the net charge enclosed by that surface? (A)The surface must enclose a negative net charge. (B)The surface must enclose a positive net charge. (C)Not enough information is given to decide.

(B)The surface must enclose a positive net charge.

*Two point charges, q1 = +q and q2 = -2q, are fixed at positions on the x-axis, as shown below. If you were to place a third point charge somewhere so that the force on it would be zero, you should place that charge at which location?* (A)on the x-axis to the right of the two charges (B)off of the x-axis (C)on the x-axis to the left of the two charges (D)on the x-axis in between the two charges

(C)

Many types of molecules may be modeled as dipoles. For example, two molecules modeled as simple dipoles are aligned on the x-axis, as shown. Each dipole consists of a positive charge q and negative charge -q, separated by a distance d. The distance between the centers of the two dipoles is x. Considering the forces due to all four charges, the net force of one dipole on the other will be which of the following? (A)repulsive (B)it depends on the relative distances d and x (C)attractive (D)zero

(C)attractive

Consider a sphere whose radius increases by 7x. How has the electric flux changed? (A)decreased (B)cannot be determined (C)the same (D)increased

(C)the same

Suppose you have a sphere of radius 1.00 m that carries a charge of +1.00 µC at its center. The radius of the sphere is changed to 0.500 m. What happens to the flux through the sphere and the magnitude of the electric field at the surface of the sphere? You can answer this without reading below. (A)The flux decreases and the field remains the same. (B)The flux and field both increase. (C)The flux increases and the field decreases. (D)The flux decreases and the field increases. (E)The flux remains the same and the field increases. (F)The flux and field both decrease.

(E)(The flux remains the same and the field increases.)

In Figure 25.1, two points A and B are located within a region in which there is an electric field. The potential difference ΔV = VB - VA is

???

In Figure 25.1, a negative charge is placed at A and the then moved to B. The change in potential energy of the charge- field system for this process is

?????

Three are brought close to each other, two at a time. When objects A and B are brought together, they attract. When objects B and C are brought together, they repel. From this, we conclude which of the following? (Select all that apply.) (A)Objects A and C possess charges of the same sign. (B)All three of the objects possess charges of the same sign. (C)One of the objects is neutral. (D)We need to perform additional tests to determine information about the charges on the objects. (E)Objects A and C possess charges of opposite sign.

ANSWER D

Object A has a charge of +2 µC, and object B has a charge of +6 µC. Which statement is true about the electric forces on the objects? (A)FAB = 3FBA (B) 3FAB = -FBA (C) 3FAB = -FBA (D) FAB = -3FBA (E) FAB = -FBA (F) FAB = FBA WHY

ANSWER E Reasons 1.VEctors 2. Newtons law of equal and oppsoite force. AB pushes B to the right(x direction) BA pushes a to the left(-x direction) -(-x)=x

Which of the following statements about electric field lines associated with electric charges is false? (A)Electric field lines can never intersect with one another. (B)Electric field lines can be either straight or curved. (C)Electric field lines can form closed loops. (D)Electric field lines begin on positive charges and end on negative charges

C

The Sun is lower in the sky during the winter than it is in the summer. How does this change the flux of sunlight hitting a given area on the surface of the Earth? How does this affect the weather?

This pertains to the the dot product equation of flux. Because it is at a angle closer to parallel to the surface, less penetration of electromagnetic waves happen. If the sun rays are perpendicular to the surface of the earth, Making the sun rays parallel to the the normal of the surface of the earth. Then the equation of involving is cos(angle 0)=1 (B) Well Less sun rays means less heat/energy. Also more darkness. So this could lead to much colder climate.

Explain why the electric flux through a closed surface with a given enclosed charge is independent of the size or shape of the surface.

couple of ways of answer this . Mathematically we have seen E has r^2 and surface area involves R^2, which these two r^2 cancel out. I have to do more research why this is the case on different

A uniform electric field exists in a region of space in which there are no charges. What can you conclude about the net electric flux through a gaussian surface placed in this region of space?

flux is zero because 1: No charge inside the enclosed area 2. as result field lines that enter also leave

A negative charge moves in the direction of a uniform electric field. Does the potential energy of the charge increase or decrease? (A) increase (B) decrease

increase

A negative charge moves in the direction of a uniform electric field. Does it move to a position of higher or lower potential? (A)lower potential (B) higher potential

lower potential

Consider the charge distribution shown in Figure 24.9. The charges contributing to the total electric flux through surface S ' are which of the following?

q2 q3

If you rub an inflated balloon against your hair, the two materials attract each other, as shown in Figure 23.3. The amount of charge present in the system of the balloon and your hair after rubbing is ___________ as the amount of charge present before rubbing.

the same