Question 1

A 5-cm radius isolated conducting sphere is charged so its potential is +100 V, relative to the potential far away. The charge density on its surface is:

Accepted Answer

A)  +2.2 * 10-7 C/m2 
B)  -2.2 * 10-7 C/m2 
C)  +3.5 *10-7 C/m2 
D)  -3.5 *10-7 C/m2 
E)  +1.8 * 10-8 C/m2 
A)  +2.2 * 10-7 C/m2 
B)  -2.2 * 10-7 C/m2 
C)  +3.5 *10-7 C/m2 
D)  -3.5 *10-7 C/m2 
E)  +1.8 * 10-8 C/m2

Question 2

Two conducting spheres, one having twice the diameter of the other, are separated by a distance large compared to their diameters. The smaller sphere (1) has charge q and the larger sphere (2) is uncharged. If the spheres are connected by a long thin wire and come to equilibrium:

Accepted Answer

A)  1 and 2 have the same potential 
B)  2 has twice the potential of 1 
C)  2 has half the potential of 1 
D)  1 and 2 have the same charge 
E)  all of the charge is dissipated 
A)  1 and 2 have the same potential 
B)  2 has twice the potential of 1 
C)  2 has half the potential of 1 
D)  1 and 2 have the same charge 
E)  all of the charge is dissipated

Question 3

A geologist measures the Earth's electric field near the surface, and finds that equipotential lines 100 V apart are at a distance of 75 cm from each other. Assuming the electric field is uniform, what is its magnitude?

Accepted Answer

A)  130 V/m 
B)  100 V/m 
C)  75 V/m 
D)  1.3 V/m 
E)  0.75 V/m 
A)  130 V/m 
B)  100 V/m 
C)  75 V/m 
D)  1.3 V/m 
E)  0.75 V/m

Question 4

The equipotential surfaces associated with a charged point particle are:

Accepted Answer

A)  radially outward from the particle 
B)  vertical planes 
C)  horizontal planes 
D)  concentric spheres centered at the particle 
E)  concentric cylinders with the particle on the axis 
A)  radially outward from the particle 
B)  vertical planes 
C)  horizontal planes 
D)  concentric spheres centered at the particle 
E)  concentric cylinders with the particle on the axis

Question 5

The work required to carry a particle with a charge of 6.0-µC from a 5.0-V equipotential surface to a 6.0-V equipotential surface and back again to the 5.0-V surface is:

Accepted Answer

A)  0 J 
B)  1.2 * 10-5 J 
C)  3.0 *10-5 J 
D)  6.0 * 10-5 J 
E)  6.0*10-6 J 
A)  0 J 
B)  1.2 * 10-5 J 
C)  3.0 *10-5 J 
D)  6.0 * 10-5 J 
E)  6.0*10-6 J

Question 6

Equipotential surfaces associated with an electric dipole are:

Accepted Answer

A)  spheres centered on the dipole 
B)  cylinders with axes along the dipole moment 
C)  planes perpendicular to the dipole moment 
D)  planes parallel to the dipole moment 
E)  none of the above 
A)  spheres centered on the dipole 
B)  cylinders with axes along the dipole moment 
C)  planes perpendicular to the dipole moment 
D)  planes parallel to the dipole moment 
E)  none of the above

Question 7

Protons in the LHC accelerator in Geneva, Switzerland are accelerated to an energy of 4.0 TeV. What is this in joules?

Accepted Answer

A)  6.4 x 10-19 J 
B)  6.4 x 10-16 J 
C)  6.4 x 10-13 J 
D)  6.4 x 10-10 J 
E)  6.4 x 10-7 J 
A)  6.4 x 10-19 J 
B)  6.4 x 10-16 J 
C)  6.4 x 10-13 J 
D)  6.4 x 10-10 J 
E)  6.4 x 10-7 J

Question 8

An electron moves from point i to point f, in the direction of a uniform electric field. During this motion:

Accepted Answer

A)  the work done by the field is positive and the potential energy of the electron-field system increases 
B)  the work done by the field is negative and the potential energy of the electron-field system increases 
C)  the work done by the field is positive and the potential energy of the electron-field system decreases 
D)  the work done by the field is negative and the potential energy of the electron-field system decreases 
E)  the work done by the field is positive and the potential energy of the electron-field system does not change 
A)  the work done by the field is positive and the potential energy of the electron-field system increases 
B)  the work done by the field is negative and the potential energy of the electron-field system increases 
C)  the work done by the field is positive and the potential energy of the electron-field system decreases 
D)  the work done by the field is negative and the potential energy of the electron-field system decreases 
E)  the work done by the field is positive and the potential energy of the electron-field system does not change

Question 9

The electric field in a region around the origin is given by , where C is a constant. The equipotential surfaces are:

Accepted Answer

A)  concentric cylinders with axes along the z axis 
B)  concentric cylinders with axes along the x axis 
C)  concentric spheres centered at the origin 
D)  planes parallel to the xy plane 
E)  planes parallel to the yz plane 
A)  concentric cylinders with axes along the z axis 
B)  concentric cylinders with axes along the x axis 
C)  concentric spheres centered at the origin 
D)  planes parallel to the xy plane 
E)  planes parallel to the yz plane

Question 10

The graph shows the electric potential as a function of x in a certain region. What is the x component of the electric field in this region if Vs = 50 V?

Accepted Answer

A)  250 V/m 
B)  40 V/m 
C)  10 V/m 
D)  -40 V/m 
E)  -250 V/m 
A)  250 V/m 
B)  40 V/m 
C)  10 V/m 
D)  -40 V/m 
E)  -250 V/m

Question 11

A particle with a charge of 5.5*10-6 C is 3.5 cm from a particle with a charge of -2.3 *10-8 C. The potential energy of this two-particle system, relative to the potential energy at infinite separation, is:

Accepted Answer

A)  3.3 * 10-2 J 
B)  -3.3* 10-2 J 
C)  9.3 * 10-1 J 
D)  -9.3 * 10-1 J 
E)  0 J 
A)  3.3 * 10-2 J 
B)  -3.3* 10-2 J 
C)  9.3 * 10-1 J 
D)  -9.3 * 10-1 J 
E)  0 J

Question 12

An electron goes from one equipotential surface to another along one of the four paths shown below. Rank the paths according to the work done by the electric field, from least to greatest.

Accepted Answer

A)  1, 2, 3, 4 
B)  4, 3, 2, 1 
C)  1, then 3, then 4 and 2 tie 
D)  4 and 2 tie, then 3, then 1 
E)  4, 3, 1, 2 
A)  1, 2, 3, 4 
B)  4, 3, 2, 1 
C)  1, then 3, then 4 and 2 tie 
D)  4 and 2 tie, then 3, then 1 
E)  4, 3, 1, 2

Exam 24: Electric Potential

A 5-cm radius isolated conducting sphere is charged so its potential is +100 V, relative to the potential far away. The charge density on its surface is:

Two conducting spheres, one having twice the diameter of the other, are separated by a distance large compared to their diameters. The smaller sphere (1) has charge q and the larger sphere (2) is uncharged. If the spheres are connected by a long thin wire and come to equilibrium:

A geologist measures the Earth's electric field near the surface, and finds that equipotential lines 100 V apart are at a distance of 75 cm from each other. Assuming the electric field is uniform, what is its magnitude?

The equipotential surfaces associated with a charged point particle are:

The work required to carry a particle with a charge of 6.0-µC from a 5.0-V equipotential surface to a 6.0-V equipotential surface and back again to the 5.0-V surface is:

Equipotential surfaces associated with an electric dipole are:

Protons in the LHC accelerator in Geneva, Switzerland are accelerated to an energy of 4.0 TeV. What is this in joules?

An electron moves from point i to point f, in the direction of a uniform electric field. During this motion:

The electric field in a region around the origin is given by , where C is a constant. The equipotential surfaces are:

The graph shows the electric potential as a function of x in a certain region. What is the x component of the electric field in this region if Vs = 50 V?

A particle with a charge of 5.5*10-6 C is 3.5 cm from a particle with a charge of -2.3 *10-8 C. The potential energy of this two-particle system, relative to the potential energy at infinite separation, is:

An electron goes from one equipotential surface to another along one of the four paths shown below. Rank the paths according to the work done by the electric field, from least to greatest.

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The graph shows the electric potential as a function of x in a certain region. What is the x component of the electric field in this region if V_s = 50 V?

A particle with a charge of 5.510^-6 C is 3.5 cm from a particle with a charge of -2.3 10^-8 C. The potential energy of this two-particle system, relative to the potential energy at infinite separation, is: