Conducting spheres and shells

A positive electric charge is moved at a constant speed between two locations in an electric field, with no work done by or against the field at any time during the motion. This situation can occur only if the

• charge is moved in the direction of the field

• charge is moved opposite to the direction of the field

• charge is moved perpendicular to an equipotential line

• charge is moved along an equipotential line

• electric field is uniform

A proton moving along the positive x-axis enters an electric field that is directed along the positive y-axis. What is the direction of the electric force acting on the proton after it enters the electric field?

• along the negative z-axis

• along the positive z-axis

• along the negative y-axis

• along the positive y-axis

• The direction cannot be determined since the magnitude of the electric field is not known

Tags

NGSS.HS-PS2-4

NGSS.HS-PS3-5

Two small spheres are arranged along a line and carry charges of +4Q and –3Q, as shown in the figure above. The vertical lines are equally spaced.

At which of the labeled points does the electric field point toward the right with the smallest magnitude?

• A

• B

• C

• D

• E

Tags

NGSS.HS-PS2-4

NGSS.HS-PS3-5

A charge +𝑄 is inside a hollow region in an electrically neutral piece of solid metal, as shown above. The dashed line represents a Gaussian surface within the metal that completely encloses the hollow region.

At which of the three labeled points is the electric field equal to zero?

• X only

• Y only

• X and Z only

• Y and Z only

• X, Y, and Z

Tags

NGSS.HS-PS2-4

The conducting sphere in Figure 1 has a charge of −Q

and is electrically isolated so that there is no conducting path to or from the conducting object shown in Figure 2. The charges on the sphere are in equilibrium. The same charge −Q

is on the isolated conducting object. Which of the following correctly describes a change between the sphere in Figure 1 and the object in Figure 2?

• The charge is no longer located entirely on the surface of the object.

• The electric field inside the object is no longer zero everywhere

• The electric potential is no longer the same at all points inside the object.

• The electric field is no longer directed perpendicular to the surface at all points on the object

• The magnitude of the electric field is no longer the same at all points on the surface

A hollow conducting sphere is surrounded by a larger concentric spherical conducting shell, as shown above. The inner sphere has a net charge of –Q, and the outer sphere has a net charge of +3Q.

What is the net charge on the outer surface of the spherical shell?

• 0

• +Q

• +2Q

• +3Q

• +4Q

Tags

NGSS.HS-PS2-4

A solid, conducting sphere with zero net charge is placed into a uniform electric field. Which of the following happens immediately after the sphere is placed in the field?

• An electric field is momentarily set up on the conducting sphere, redistributing the charges until the surface again becomes equipotential.

• A nonuniform electric field is permanently set up inside the conducting sphere, pushing charges to the surface of the sphere.

• The electric field aligns the charges inside the sphere in such a way that they create a uniform electric field inside the sphere that is equivalent to the external electric field.

• The electric field does not interact with the sphere since it has zero net charge.

When two metal objects, X and Y, are connected to each other by a conducting wire, object X gains electrons. From this information, it can be inferred that before the connection was made, object X, compared with object Y, must have had

• less capacitance

• more electrical potential energy

• a greater electric charge

• a greater electric potential

A uniform electric field exists in which of the following regions?

I. Around an infinite line of uniform linear charge density

II. On either side of an infinite thin sheet of uniform charge density

III. Between the spherical shells of a charged spherical capacitor

• I only

• II only

• III only

• II and III only

• I, II, and III

The figure above shows an object in the shape of an arc. The object has a uniform charge distribution. The three labeled vectors show possible directions of the electric field at point P

at the center of the arc. Which of the following options indicates the vector that shows the correct direction of the electric field and provides a correct physical explanation for this direction?

• Vector A: the charge distribution is positive, and there are more charges to the left of point P

  .

• Vector A: the charge distribution is negative, and there are more charges to the left of point P

  .

• Vector B: the charge distribution is positive, and there are more charges above point P

  .

• Vector B: the charge distribution is negative, and there are more charges above point P

  .

• Vector C: the charge distribution is positive, and there are no charges below and to the left of point P

  to cancel the field from charges above and to the right of point P

  .

Tags

NGSS.HS-PS2-4