Question 1

A charged particle of mass $10 ^ { - 26 }$ kg is released in a uniform electric field of 1.3 pN/C. The acceleration of the charge is 9100 m/s $2$ Therefore the charge is

Accepted Answer

A)  70 pC. 
B)  18 pC. 
C)  3.5 pC. 
D)  40 pC. 
A)  70 pC. 
B)  18 pC. 
C)  3.5 pC. 
D)  40 pC. A

Question 2

Consider a positively charged square plate of finite size (a few centimeters on edge). Point P lies in the same plane as the plate and is a few centimeters away from one edge of the plate. If point P were moved slightly away (parallel with the plane), the magnitude of the E-field (compared to its direction before the movement of P) would

Accepted Answer

A)  increase monotonically (continually) but not uniformly. 
B)  increase at first, then decrease. 
C)  decrease monotonically (continually) but not uniformly. 
D)  decrease at first, then increase. 
A)  increase monotonically (continually) but not uniformly. 
B)  increase at first, then decrease. 
C)  decrease monotonically (continually) but not uniformly. 
D)  decrease at first, then increase. C

Question 3

An electric dipole may experience all of the following except

Accepted Answer

A)  a force in a uniform E-field. 
B)  a torque in a uniform E-field. 
C)  a force in a nonuniform E-field. 
D)  a torque in a nonuniform E-field. 
A)  a force in a uniform E-field. 
B)  a torque in a uniform E-field. 
C)  a force in a nonuniform E-field. 
D)  a torque in a nonuniform E-field. A

Question 4

As the location of interest is moved farther away from an infinite plane possessing constant charge per area, the E-field

Accepted Answer

A)  does not change. 
B)  increases at first, then decreases. 
C)  decreases at first, then increases. 
D)  changes monotonically (continually) but not uniformly. 
A)  does not change. 
B)  increases at first, then decreases. 
C)  decreases at first, then increases. 
D)  changes monotonically (continually) but not uniformly.

Question 5

An infinite flat sheet has a surface charge density of $- 15.3$ nC/m $2$ The direction of the electric field at a distance of 5.3 cm above the infinite sheet

Accepted Answer

A)  is parallel with the surface of the sheet. 
B)  is perpendicular and pointing away from the sheet. 
C)  is perpendicular and pointing toward the sheet. 
D)  cannot be determined. 
A)  is parallel with the surface of the sheet. 
B)  is perpendicular and pointing away from the sheet. 
C)  is perpendicular and pointing toward the sheet. 
D)  cannot be determined.

Question 6

The E-field at point P for each of the following is zero except for the case of

Accepted Answer

A)  any two-dimensional regular polygon (such as an equilateral triangle or a square), P at the geometric center, an identical charge at each vertex. 
B)  any three-dimensional regular solid (such as a cube or a tetrahedron), P at the geometric center, an identical charge at each vertex. 
C)  any two-dimensional regular polygon with an even number of sides (such as a square or hexagon), P at the geometric center, identical charges (of either sign) at each of a pair of vertices opposite each other. 
D)  Hold it! There are no exceptions. 
A)  any two-dimensional regular polygon (such as an equilateral triangle or a square), P at the geometric center, an identical charge at each vertex. 
B)  any three-dimensional regular solid (such as a cube or a tetrahedron), P at the geometric center, an identical charge at each vertex. 
C)  any two-dimensional regular polygon with an even number of sides (such as a square or hexagon), P at the geometric center, identical charges (of either sign) at each of a pair of vertices opposite each other. 
D)  Hold it! There are no exceptions.

Question 7

An infinitely long wire has a linear charge density of 1.8 nC/m. The magnitude of the electric field two meters away from the wire is

Accepted Answer

A)  32 N/C. 
B)  64 N/C. 
C)  16 N/C. 
D)  56 N/C. 
A)  32 N/C. 
B)  64 N/C. 
C)  16 N/C. 
D)  56 N/C.

Question 8

A 13.6-N force is acting on an electrical charge. At the location of the charge, the 3.1-N/C electric field points in the opposite direction of the force. The charge is

Accepted Answer

A)  $+ 4.4 \mathrm { C } \text {. }$ 
B)  $- 4.4 \mathrm { C }$ 
C)  $- 230$ mC. 
D)  $+ 230$ mC. 
A)  $+ 4.4 \mathrm { C } \text {. }$ 
B)  $- 4.4 \mathrm { C }$ 
C)  $- 230$ mC. 
D)  $+ 230$ mC.

Question 9

A wire has a linear charge density $\lambda ( x ) = 2.35 x$ , where $x$ is in meters (m) and $\lambda$ is in C/m. If the length of the wire is 3.7 m, the total charge on the wire is

Accepted Answer

A)  11 C. 
B)  1.2 C. 
C)  16 C. 
D)  8.0 C. 
A)  11 C. 
B)  1.2 C. 
C)  16 C. 
D)  8.0 C.

Question 10

Two electrons are in close proximity; the repulsive force between them is 1.1 $\mu$ N. The distance between the two charges is

Accepted Answer

A)  $3.5 \times 10 ^ { - 11 }$ m. 
B)  $7.8 \times 10 ^ { - 11 }$ m. 
C)  $1.4 \times 10 ^ { - 11 }$ m. 
D)  $5.3 \times 10 ^ { - 11 }$ m. 
A)  $3.5 \times 10 ^ { - 11 }$ m. 
B)  $7.8 \times 10 ^ { - 11 }$ m. 
C)  $1.4 \times 10 ^ { - 11 }$ m. 
D)  $5.3 \times 10 ^ { - 11 }$ m.

Question 11

Consider a positively charged wire bent into the shape of a capital "U". Point P is down in the well of the "U" (specifically at the center of curvature). At point P, the direction of the E-field is

Accepted Answer

A)  toward the top of the page. 
B)  toward the bottom of the page. 
C)  toward the right of the page. 
D)  toward the left of the page. 
A)  toward the top of the page. 
B)  toward the bottom of the page. 
C)  toward the right of the page. 
D)  toward the left of the page.

Question 12

The final (stable) orientation of an electric dipole in a E-field occurs when the torque $\tau$ on the dipole and the potential energy U of the dipole are arranged as follows:

Accepted Answer

A)  $\tau$ is a maximum and U is a minimum. 
B)  $\tau$ is a minimum and U is zero. 
C)  $\tau$ is zero and U is a minimum. 
D)  $\tau$ is zero and U is zero. 
A)  $\tau$ is a maximum and U is a minimum. 
B)  $\tau$ is a minimum and U is zero. 
C)  $\tau$ is zero and U is a minimum. 
D)  $\tau$ is zero and U is zero.

Question 13

A dipole moment is embedded in an external electric field. The direction of the torque acting on the dipole is

Accepted Answer

A)  from the negative charge towards the positive charge. 
B)  given by the right-hand rule. 
C)  given by the left-hand rule. 
D)  from the positive charge toward the negative charge. 
A)  from the negative charge towards the positive charge. 
B)  given by the right-hand rule. 
C)  given by the left-hand rule. 
D)  from the positive charge toward the negative charge.

Question 14

E-field lines are correctly described by all of the following except

Accepted Answer

A)  they are more concentrated in regions where the field strength is greater. 
B)  they are continuous in regions containing no charge. 
C)  they trace out the path (direction reversed) that would be followed by an electron (with mass) placed in the field and released. 
D)  they are analogous to streamlines for fluid flow. 
A)  they are more concentrated in regions where the field strength is greater. 
B)  they are continuous in regions containing no charge. 
C)  they trace out the path (direction reversed) that would be followed by an electron (with mass) placed in the field and released. 
D)  they are analogous to streamlines for fluid flow.

Question 15

A proton is released from rest in the presence of a static uniform electric field of 18 $\mu$ N/C. The velocity of the proton at four seconds is

Accepted Answer

A)  8.6 m/s. 
B)  1200 m/s. 
C)  560 m/s. 
D)  6900 m/s. 
A)  8.6 m/s. 
B)  1200 m/s. 
C)  560 m/s. 
D)  6900 m/s.

Question 16

Consider a positively charged square plate of finite size (a few centimeters on edge). Point P' is centered a few centimeters above the plate. If point P' were moved slightly to the left, the direction of the E-field at point P' would (compared to its direction before the movement)

Accepted Answer

A)  shift slightly toward the right of the plate. 
B)  shift slightly toward the left of the plate. 
C)  shift slightly out of the plane of the plate. 
D)  Hold it! None of the above answers is correct. 
A)  shift slightly toward the right of the plate. 
B)  shift slightly toward the left of the plate. 
C)  shift slightly out of the plane of the plate. 
D)  Hold it! None of the above answers is correct.

Question 17

All of the following statements are true of E-field lines except

Accepted Answer

A)  they start and stop on charges. 
B)  they cannot exist in a vacuum. 
C)  they obey the superposition principle. 
D)  they point in the direction of the force on a positive test charge. 
A)  they start and stop on charges. 
B)  they cannot exist in a vacuum. 
C)  they obey the superposition principle. 
D)  they point in the direction of the force on a positive test charge.

Question 18

In a nonuniform E-field, an electric dipole free to rotate and free to translate will be

Accepted Answer

A)  drawn in a direction of stronger E-field. 
B)  drawn in a direction of weaker E-field. 
C)  rotated, but not drawn in any direction with respect to the E-field. 
D)  Hold it! None of the above answers is correct in general. 
A)  drawn in a direction of stronger E-field. 
B)  drawn in a direction of weaker E-field. 
C)  rotated, but not drawn in any direction with respect to the E-field. 
D)  Hold it! None of the above answers is correct in general.

Question 19

A proton is released from rest in the presence of a static uniform electric field of 18 $\mu$ N/C. The change in the position of the proton at four seconds is

Accepted Answer

A)  7.8 km. 
B)  14 km. 
C)  1.3 km. 
D)  2.6 km. 
A)  7.8 km. 
B)  14 km. 
C)  1.3 km. 
D)  2.6 km.

Question 20

Two equal charges are separated by 5 cm; the repulsive force is found to be 2.5 N. The magnitude of one of the charges is

Accepted Answer

A)  $8.3 \times 10 ^ { - 7 } \mathrm { C }$ 
B)  - $7.6 \times 10 ^ { - 13 } \mathrm { C }$ 
C)  $9.4 \times 10 ^ { - 7 } \mathrm { C }$ 
D)  $6.9 \times 10 ^ { - 13 } \mathrm { C }$ 
A)  $8.3 \times 10 ^ { - 7 } \mathrm { C }$ 
B)  - $7.6 \times 10 ^ { - 13 } \mathrm { C }$ 
C)  $9.4 \times 10 ^ { - 7 } \mathrm { C }$ 
D)  $6.9 \times 10 ^ { - 13 } \mathrm { C }$

Exam 23: The Electric Field

A charged particle of mass 10−2610 ^ { - 26 }10−26 kg is released in a uniform electric field of 1.3 pN/C. The acceleration of the charge is 9100 m/s 222 Therefore the charge is

An electric dipole may experience all of the following except

As the location of interest is moved farther away from an infinite plane possessing constant charge per area, the E-field

An infinite flat sheet has a surface charge density of −15.3- 15.3−15.3 nC/m 222 The direction of the electric field at a distance of 5.3 cm above the infinite sheet

The E-field at point P for each of the following is zero except for the case of

An infinitely long wire has a linear charge density of 1.8 nC/m. The magnitude of the electric field two meters away from the wire is

A 13.6-N force is acting on an electrical charge. At the location of the charge, the 3.1-N/C electric field points in the opposite direction of the force. The charge is

A wire has a linear charge density λ(x)=2.35x\lambda ( x ) = 2.35 xλ(x)=2.35x , where xxx is in meters (m) and λ\lambdaλ is in C/m. If the length of the wire is 3.7 m, the total charge on the wire is

Two electrons are in close proximity; the repulsive force between them is 1.1 μ\muμ N. The distance between the two charges is

Consider a positively charged wire bent into the shape of a capital "U". Point P is down in the well of the "U" (specifically at the center of curvature). At point P, the direction of the E-field is

The final (stable) orientation of an electric dipole in a E-field occurs when the torque τ\tauτ on the dipole and the potential energy U of the dipole are arranged as follows:

A dipole moment is embedded in an external electric field. The direction of the torque acting on the dipole is

E-field lines are correctly described by all of the following except

A proton is released from rest in the presence of a static uniform electric field of 18 μ\muμ N/C. The velocity of the proton at four seconds is

Consider a positively charged square plate of finite size (a few centimeters on edge). Point P' is centered a few centimeters above the plate. If point P' were moved slightly to the left, the direction of the E-field at point P' would (compared to its direction before the movement)

All of the following statements are true of E-field lines except

In a nonuniform E-field, an electric dipole free to rotate and free to translate will be

A proton is released from rest in the presence of a static uniform electric field of 18 μ\muμ N/C. The change in the position of the proton at four seconds is

Two equal charges are separated by 5 cm; the repulsive force is found to be 2.5 N. The magnitude of one of the charges is

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