Exam 1 Practice

Two point charges, initially 2.0 cm apart, experience a 1.0-N force. If they are moved to a new separation of 8.0 cm, what is the electric force between them?

 A. 4.0 N B. 16 N C. 1/4 N D. 1/16 N

Sphere A carries a net charge and sphere B is neutral. They are placed near each other on an insulated table. Which statement best describes the electrostatic force between them?

 A. There is no force between them since one is neutral. B. There is a force of repulsion between them. C. There is a force of attraction between them. D. The force is attractive if A is charged positively and repulsive if A is charged negatively.

Three identical point charges of 2.0 æC are placed on the x-axis. The first charge is at the origin, the second to the right at x = 50 cm, and the third is at the 100 cm mark. What are the magnitude and direction of the electrostatic force which acts on the charge at the origin?

 A. 0.18 N left B. 0.18 N right C. 0.36 N left D. 0.36 N right

Electric field lines

 A. circle clockwise around positive charges. B. circle counter-clockwise around positive charges. C. radiate outward from negative charges. D. radiate outward from positive charges.

A force of 6.0 N acts on a charge of 3.0 æC when it is placed in a uniform electric field. What is the magnitude of this electric field?

 A. 18 MN/C B. 2.0 MN/C C. 0.50 MN/C D. 130 MN/C

A 5.0-C charge is 10 m from a small test charge of 1.0 nC. What is the direction of the electric field at the 1.0 nC charge?

 A. toward the 5.0 C B. away from the 5.0 C C. perpendicular to a line joining the charges D. none of the above

A 5.0-æC charge is placed at the 0 cm mark of a meterstick and a -4.0 æC charge is placed at the 50 cm mark. At what point on a line joining the two charges is the electric field zero?

 A. 1.4 m from the 0 cm mark B. 2.9 m from the 0 cm mark C. 3.3 m from the 0 cm mark D. 4.7 m from the 0 cm mark

A metal sphere of radius 10 cm carries a charge of +2.0 æC. What is the magnitude of the electric field 5.0 cm from the sphere's surface?

 A. 4.0X105 N/C B. 8.0X105 N/C C. 4.0X107 N/C D. 8.0X107 N/C

The net work done in moving an electron from point A, where the potential is -50 V, to point B, where the potential is +50 V, is

 A. +1.6X10-17 J B. -1.6X10-17 J C. zero D. none of the above.

Starting from rest, a proton falls through a potential difference of 1200 V. What speed does it acquire?

 A. 1.2X105 m/s B. 2.4X105 m/s C. 3.6X105 m/s D. 4.8X105 m/s

For an electron moving in a direction opposite to the electric field

 A. its potential energy increases and its potential decreases. B. its potential energy decreases and its potential increases. C. its potential energy increases and its potential increases. D. its potential energy decreases and its potential decreases.

How much work does 9.0 V do in moving 8.5X1018 electrons?

 A. 12 J B. 7.7 J C. 1.4 J D. 1.1 J

A uniform electric field, with a magnitude of 500 V/m, is directed parallel to the +x axis. If the potential at x = 5.0 m is 2500 V, what is the potential at x = 2.0 m?

 A. 500 V B. 1000 V C. 2000 V D. 4000 V

The absolute potential at a distance of 2.0 m from a negative point charge is -100 V. What is the absolute potential 4.0 m away from the same point charge?

 A. -25 V B. -50 V C. -200 V D. -400 V

The absolute potential at the center of a square is 3.0 V when a charge of +Q is located at one of the square's corners. What is the absolute potential at the square's center when a second charge of -Q is placed at one of the remaining corners?

 A. zero B. 3.0 V C. 6.0 V D. 9.0 V

A parallel-plate capacitor consists of plates of area 1.5X10-4 m2 and separated by 1.0 mm. The capacitor is connected to a 12-V battery. What is the charge on the plates?

 A. 1.6X10-11 C B. 3.2X10-11 C C. 1.6X10-14 C D. 3.2X10-14 C

A parallel plate capacitor is constructed with plate area of 0.40 m2 and a plate separation of 0.10 mm. How much charge is stored on it when it is charged to a potential difference of 12 V?

 A. 0.21 æC B. 0.42 æC C. 0.63 æC D. 0.84 æC

A parallel plate capacitor is constructed with plate area of 0.40 m2 and a plate separation of 0.10 mm. How much energy is stored?

 A. 2.5 æJ B. 5.0 æJ C. 7.5 æJ D. 10 æJ

A 15-æF capacitor is connected to a 50-V battery and becomes fully charged. The battery is removed and a slab of dielectric that completely fills the space between the plates is inserted. If the dielectric has a dielectric constant of 5.0, what is the capacitance of the capacitor after the slab is inserted?

 A. 75 æF B. 20 æF C. 3.0 æF D. 1.0 æF

A 15-æF capacitor is connected to a 50-V battery and becomes fully charged. The battery is removed and a slab of dielectric that completely fills the space between the plates is inserted. If the dielectric has a dielectric constant of 5.0, what is the voltage across the capacitor's plates after the slab is inserted?

 A. 250 V B. 10 V C. 2.0 V D. 0.75 V