Question 1

A proton with speed 1.5 × 105 m/s falls through a potential difference of 100 volts,gaining speed.What is the speed reached?

Accepted Answer

A) 4.56 × 105 m/s 
B) 2.04 × 105 m/s 
C) 3.55 × 105 m/s 
D) 8.80 × 105 m/s 
E) 1.55 × 106 m/s 
A) 4.56 × 105 m/s 
B) 2.04 × 105 m/s 
C) 3.55 × 105 m/s 
D) 8.80 × 105 m/s 
E) 1.55 × 106 m/s B

Question 2

Four charged particles (two having a charge +Q and two having a charge -Q)are distributed on the xy-plane,as shown below.Each charge is equidistant from the origin.The voltage is zero at infinity.The voltage at location P,which is on the z axis,is

Accepted Answer

A) zero. 
B) positive. 
C) negative. 
D) impossible to determine based on the information given. 
A) zero. 
B) positive. 
C) negative. 
D) impossible to determine based on the information given. A

Question 3

A parallel-plate capacitor consists of two parallel,square plates that have dimensions 1.0 cm by 1.0 cm.If the plates are separated by 1.0 mm,and the space between them is filled with teflon,what is the capacitance? (The dielectric constant for teflon is 2.1. )

Accepted Answer

A) 1.9 pF 
B) 0.44 pF 
C) 2.1 pF 
D) 0.88 pF 
A) 1.9 pF 
B) 0.44 pF 
C) 2.1 pF 
D) 0.88 pF A

Question 4

A dipole with ±6.0 μC charges is positioned so that the positive charge is 1.0 mm to the right of the origin and the negative charge is at the origin.How much work does it take to bring a 10.0 μC charge from infinity to a position x = 3.0 mm,y = 0.0 mm? (The value of k is 9.0 F1F1F1S1F1F1F10 109 N·m2/C2. )

Accepted Answer

A) 90 J 
B) 450 J 
C) 75 J 
D) 200 J 
A) 90 J 
B) 450 J 
C) 75 J 
D) 200 J

Question 5

Two parallel plates are separated by 1.0 mm.If the potential difference between them is 3.0 V,what is the magnitude of their surface charge densities?

Accepted Answer

A) 27 nC/m2 
B) 0.16 mC/m2 
C) 53 nC/m2 
D) 0.33 mC/m2 
A) 27 nC/m2 
B) 0.16 mC/m2 
C) 53 nC/m2 
D) 0.33 mC/m2

Question 6

If an object is at zero potential,it must be uncharged.

Accepted Answer

A) True 
 B)False

Question 7

A 6.0 μC negative charge is attracted to a large,well-anchored,positive charge.How much kinetic energy does the negatively charged object gain if the potential difference through which it moves is 3 mV?

Accepted Answer

A) 18 nJ 
B) 0.50 kJ 
C) 0.50 J 
D) 6.0 μJ 
A) 18 nJ 
B) 0.50 kJ 
C) 0.50 J 
D) 6.0 μJ

Question 8

When the electric field is zero at a point,the potential must also be zero there.

Accepted Answer

A) True 
 B)False

Question 9

A uniform electric field has the strength of 5.0 N/C.What is the electric energy density of the field? (The value of εo is 8.85 F1F1F1S1F1F1F10 10-12 C2/N·m2. )

Accepted Answer

A) 1.1 × 10-10 J/m3 
B) 2.2 × 10-11 J/m3 
C) 1.4 × 1012 J/m3 
D) 2.8 × 1012 J/m3 
A) 1.1 × 10-10 J/m3 
B) 2.2 × 10-11 J/m3 
C) 1.4 × 1012 J/m3 
D) 2.8 × 1012 J/m3

Question 10

A 3.0 μC point charge and a 9.0 μC point charge are initially infinitely far apart.How much work does it take to bring the 3.0 μC point charge to x = 3.0 mm,y = 0.0 mm,and the 9.0 μC point charge to x = -3.0 mm,y = 0.0 mm? (The value of k is 9.0 F1F1F1S1F1F1F10 109 N·m2/C2. )

Accepted Answer

A) 41 J 
B) 81 J 
C) 27 J 
D) 6.8 J 
A) 41 J 
B) 81 J 
C) 27 J 
D) 6.8 J

Question 11

A proton with a speed of 2.0 x 105 m/s falls through a potential difference V and thereby increases its speed to 4.0 × 105 m/s.Through what potential difference did the proton fall?

Accepted Answer

A) 630 V 
B) 210 V 
C) 840 V 
D) 1000 V 
E) 100 V 
A) 630 V 
B) 210 V 
C) 840 V 
D) 1000 V 
E) 100 V

Question 12

Suppose you have two positive point charges and want to move them closer together.To do the least amount of work,you should move them directly toward each other;any other path will require more work because the charges must move through a greater distance.

Accepted Answer

A) True 
 B)False

Question 13

If the electrical potential in a region is constant,the electric field must be zero everywhere in that region.

Accepted Answer

A) True 
 B)False

Question 14

Two equal but opposite point charges are held a distance D apart,and a third point charge Q is placed midway between them.When Q is released it will remain at rest because its potential energy is zero at the midpoint.

Accepted Answer

A) True 
 B)False

Question 15

If the voltage at a point in space is zero,then the electric field must be

Accepted Answer

A) negative. 
B) zero. 
C) uniform. 
D) positive. 
E) Impossible to determine based on the information given. 
A) negative. 
B) zero. 
C) uniform. 
D) positive. 
E) Impossible to determine based on the information given.

Question 16

As an electron moves from a high potential to a low potential,its electrical potential energy

Accepted Answer

A) increases. 
B) decreases. 
C) remains constant. 
A) increases. 
B) decreases. 
C) remains constant.

Question 17

Three charges form an equilateral triangle with 1.6 cm long sides.What is the electric potential at the point indicated with the dot?

Accepted Answer

A) zero 
B) 3900 V 
C) 1900 V 
D) 5800 V 
A) zero 
B) 3900 V 
C) 1900 V 
D) 5800 V

Question 18

A 3.0 pF capacitor consists of two parallel plates that have surface charge densities of ±1.0 nC/mm2.If the potential between the plates is 23.0 kV,find the surface area of one of the plates.

Accepted Answer

A) 69 mm2 
B) 0.014 mm2 
C) 35 mm2 
D) 0.0072 mm2 
A) 69 mm2 
B) 0.014 mm2 
C) 35 mm2 
D) 0.0072 mm2

Question 19

A small object carries a charge of 10.0 μC.If the object is so small that it can be regarded as a point charge,what is the energy density at a distance of 2.0 m from the charge? (The value of k is 9.0 F1F1F1S1F1F1F10 109 N·m2/C2. )

Accepted Answer

A) 2.2 mJ/m3 
B) 4.5 mJ/m3 
C) 9.0 mJ/m3 
D) 18 mJ/m3 
A) 2.2 mJ/m3 
B) 4.5 mJ/m3 
C) 9.0 mJ/m3 
D) 18 mJ/m3

Question 20

Four identical positive point charges lie at the corners of a square.The electrical potential at the center of this square is zero because the electric fields all cancel at that point.

Accepted Answer

A) True 
 B)False

Exam 21: Electric Potential

A proton with speed 1.5 × 105 m/s falls through a potential difference of 100 volts,gaining speed.What is the speed reached?

Four charged particles (two having a charge +Q and two having a charge -Q)are distributed on the xy-plane,as shown below.Each charge is equidistant from the origin.The voltage is zero at infinity.The voltage at location P,which is on the z axis,is

A parallel-plate capacitor consists of two parallel,square plates that have dimensions 1.0 cm by 1.0 cm.If the plates are separated by 1.0 mm,and the space between them is filled with teflon,what is the capacitance? (The dielectric constant for teflon is 2.1. )

A dipole with ±6.0 μC charges is positioned so that the positive charge is 1.0 mm to the right of the origin and the negative charge is at the origin.How much work does it take to bring a 10.0 μC charge from infinity to a position x = 3.0 mm,y = 0.0 mm? (The value of k is 9.0  109 N·m2/C2. )

Two parallel plates are separated by 1.0 mm.If the potential difference between them is 3.0 V,what is the magnitude of their surface charge densities?

If an object is at zero potential,it must be uncharged.

A 6.0 μC negative charge is attracted to a large,well-anchored,positive charge.How much kinetic energy does the negatively charged object gain if the potential difference through which it moves is 3 mV?

When the electric field is zero at a point,the potential must also be zero there.

A uniform electric field has the strength of 5.0 N/C.What is the electric energy density of the field? (The value of εo is 8.85  10-12 C2/N·m2. )

A 3.0 μC point charge and a 9.0 μC point charge are initially infinitely far apart.How much work does it take to bring the 3.0 μC point charge to x = 3.0 mm,y = 0.0 mm,and the 9.0 μC point charge to x = -3.0 mm,y = 0.0 mm? (The value of k is 9.0  109 N·m2/C2. )

A proton with a speed of 2.0 x 105 m/s falls through a potential difference V and thereby increases its speed to 4.0 × 105 m/s.Through what potential difference did the proton fall?

Suppose you have two positive point charges and want to move them closer together.To do the least amount of work,you should move them directly toward each other;any other path will require more work because the charges must move through a greater distance.

If the electrical potential in a region is constant,the electric field must be zero everywhere in that region.

Two equal but opposite point charges are held a distance D apart,and a third point charge Q is placed midway between them.When Q is released it will remain at rest because its potential energy is zero at the midpoint.

If the voltage at a point in space is zero,then the electric field must be

As an electron moves from a high potential to a low potential,its electrical potential energy

Three charges form an equilateral triangle with 1.6 cm long sides.What is the electric potential at the point indicated with the dot?

A 3.0 pF capacitor consists of two parallel plates that have surface charge densities of ±1.0 nC/mm2.If the potential between the plates is 23.0 kV,find the surface area of one of the plates.

A small object carries a charge of 10.0 μC.If the object is so small that it can be regarded as a point charge,what is the energy density at a distance of 2.0 m from the charge? (The value of k is 9.0  109 N·m2/C2. )

Four identical positive point charges lie at the corners of a square.The electrical potential at the center of this square is zero because the electric fields all cancel at that point.

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A proton with speed 1.5 × 10⁵ m/s falls through a potential difference of 100 volts,gaining speed.What is the speed reached?

A uniform electric field has the strength of 5.0 N/C.What is the electric energy density of the field? (The value of εo is 8.85  10-12 C²/N·m². )

A 3.0 μC point charge and a 9.0 μC point charge are initially infinitely far apart.How much work does it take to bring the 3.0 μC point charge to x = 3.0 mm,y = 0.0 mm,and the 9.0 μC point charge to x = -3.0 mm,y = 0.0 mm? (The value of k is 9.0  10⁹ N·m²/C². )

A proton with a speed of 2.0 x 10⁵ m/s falls through a potential difference V and thereby increases its speed to 4.0 × 10⁵ m/s.Through what potential difference did the proton fall?

A 3.0 pF capacitor consists of two parallel plates that have surface charge densities of ±1.0 nC/mm².If the potential between the plates is 23.0 kV,find the surface area of one of the plates.

A small object carries a charge of 10.0 μC.If the object is so small that it can be regarded as a point charge,what is the energy density at a distance of 2.0 m from the charge? (The value of k is 9.0  10⁹ N·m²/C². )