Question 1

In Millikan's oil drop experiment,if the electric field between the plates was of just the right magnitude,it would exactly balance the weight of the drop.Suppose a tiny spherical oil droplet of radius 1.3 × 10−⁴ cm carries a charge equivalent to one electron.What electric field is required to balance the weight? (The density of oil is 0.85 g/cm³,e = 1.6 × 10−¹⁹ C. )

Accepted Answer

The answer of In Millikan's oil drop experiment,if the electric...

Question 2

We have an initially uncharged hollow metallic sphere with radius of 5.0 cm.I place a small object with a charge of +20 µC at the center of the sphere through a hole in the surface.Find the electric field present at a point 10 cm from the sphere's center.(k_e = 8.99 × 10⁹ N⋅m²/C²)

Accepted Answer

The answer of We have an initially uncharged hollow metallic...

Question 3

If a charge +Q is placed inside a hollow isolated conductor that is originally neutral and the charge does not touch that conductor at any time:

Accepted Answer

When a charge +Q is placed inside a hollow isolated conductor, it induces an equal but opposite charge on the inner surface of the conductor, leaving the outer surface with a net positive charge equal in magnitude to the charge placed inside. The inner surface becomes negatively charged to balance the internal field, ensuring the field inside the conductor's material remains zero.

Question 4

In the Millikan oil-drop experiment it was found that oil droplets:

Accepted Answer

In the Millikan oil-drop experiment, it was found that oil droplets could have positive, negative, or zero net charge. This was determined by measuring the rate at which the droplets fell in the presence of an electric field, which was dependent on their charge. Therefore, choice D is the correct answer.

Question 5

The Millikan oil-drop experiment demonstrated that:

Accepted Answer

The Millikan oil-drop experiment demonstrated that the electronic charge is quantized, meaning that it exists in discrete units rather than being continuous. This was shown by observing the behavior of oil droplets suspended in an electric field, and carefully measuring the forces acting on them. The results provided the first accurate determination of the fundamental charge of an electron.

Question 6

Relative distribution of charge density on the surface of a conducting solid depends on the

Accepted Answer

The shape of the conductor determines the distribution of charge density on its surface. The charges will distribute themselves in such a way that the electric field inside the conductor is zero, and the charges will reside on the surface of the conductor. This redistribution of charges will depend on the shape of the conductor.

Question 7

Two identical iron spheres have equal positive charges and the force between them when they are 1 m apart is 2 N.What percentage of the electrons has been removed from each sphere if each sphere has 1 mole (6 × 10²³)of iron atoms? (k_e = 8.99 × 10⁹ N⋅m²/C²,the atomic number of iron is 26,and the electron charge is −1.6 × 10−¹⁹ C)

Accepted Answer

The answer of Two identical iron spheres have equal positive...

Question 8

Two identical balls have the same amount of charge,but the charge on ball A is positive and the charge on ball B is negative.The balls are placed on a smooth,level,frictionless table whose top is an insulator.Which of the following is true?

Accepted Answer

Although the balls have the same amount of charge, they have opposite signs. So, they will attract each other with the same magnitude of force. This means that they will move towards each other until they meet at the middle point. After that, they will stick together and become neutral. Therefore, none of the above choices is correct.

Question 9

We have a hollow metallic sphere with charge −5.20 µC and radius 5.40 cm.We insert a +10.4-µC charge at the center of the sphere through a hole in the surface.What charge now rests on the outer surface of the sphere?​

Accepted Answer

Since the charge is inserted at the center of the sphere, it will be equally distributed on the inner surface of the sphere due to the symmetry of the problem. As a result, there will be no charge on the outer surface of the sphere before the charge is inserted.

After the charge is inserted, the total charge inside the sphere becomes -5.20 µC + 10.4 µC = 5.20 µC, due to the conservation of charge. Since the total charge is positive, the same amount of charge must be induced on the outer surface of the sphere to cancel out the electric field inside the sphere. Therefore, the answer is A) +5.20 µC.

Question 10

A ping-pong ball covered with a conducting graphite coating has a mass of 5.4 × 10−³ kg and a charge of 3.8 µC.What electric field directed upward will exactly balance the weight of the ball? (g = 9.8 m/s²)

Accepted Answer

To balance the weight of the ball, the electric force (F_e) must equal the gravitational force (F_g). The gravitational force is given by F_g = m*g, where m is the mass and g is the acceleration due to gravity. The electric force is given by F_e = q*E, where q is the charge and E is the electric field. Setting F_g = F_e gives m*g = q*E. Solving for E gives E = (m*g)/q. Substituting the given values (m = 5.4 × 10^-3 kg, g = 9.8 m/s^2, q = 3.8 × 10^-6 C) yields E ≈ 1.4 × 10^4 N/C.

Question 11

An initially uncharged hollow metallic sphere with radius of 5 cm has a small object with a charge of +15 µC carefully placed at the center of the sphere through a hole in the latter's surface.What charge resides inner surface of the sphere?

Accepted Answer

The charge on the inner surface of the sphere will be -15 µC to neutralize the effect of the +15 µC charge placed at the center, ensuring the electric field inside the conductor is zero.

Question 12

Two identical spheres each carry a charge of −82.0 µC.The spheres are separated by a distance of 2.00 m.What is the electric force between the spheres? (k_e = 8.99 × 10⁹ N·m²/C²)

Accepted Answer

The electric force between two charges is given by Coulomb's law:
F = k(q1q2)/r^2
where k is the Coulomb constant, q1 and q2 are the charges, and r is the distance between them.

Substituting the given values,

F = (8.99 × 10^9 N·m^2/C^2)(-82.0 × 10^-6 C)^2/(2.00 m)^2

F = 15.1 N (repulsive)

Therefore, the electric force between the spheres is 15.1 N and it is repulsive because both spheres carry the same charge. Hence, the best choice is B.

Question 13

The electric field at the surface of a positively charged conductor has a direction characterized by which of the following?

Accepted Answer

At the surface of a positively charged conductor, the electric field is perpendicular outward and away from the charge. This is because like charges repel each other, causing the electric field lines to spread out away from the surface of the conductor.

Question 14

An initially uncharged hollow metallic sphere with radius of 6 cm has a small object with a charge of +14 µC carefully placed at the center of the sphere through a hole in the latter's surface.With the charge in place,what charge is now present on the outside surface of the sphere?​

Accepted Answer

According to the principle of electrostatics, the charge on the outer surface of a conductor is always located on its surface. Therefore, the charge on the outer surface of this initially uncharged hollow metallic sphere will be induced by the +14 µC charge placed at the center of the sphere.

Since the sphere is metallic, the charge distribution on its surface will be such that the electric field inside it is zero. Therefore, the charge on the outer surface of the sphere will be -14 µC, which is equal in magnitude but opposite in sign to the +14 µC charge placed at the center of the sphere.

Hence, the answer is D, +14 µC.

Question 15

The electric field associated with a uniformly charged hollow metallic sphere is the greatest at:

Accepted Answer

The electric field inside a hollow metallic sphere is zero due to the shielding effect of the surface charge. Therefore, the greatest electric field must be at the sphere's outer surface, where the charge is concentrated.

Question 16

At what point is the charge per unit area greatest on the surface of an irregularly shaped conducting solid?

Accepted Answer

The charge per unit area (surface charge density) on an irregularly shaped conducting solid is greatest where the curvature is greatest. This is because electric field lines are more concentrated in areas of high curvature, leading to a higher accumulation of charge in these regions.

Question 17

Two point charges,one ​q and the other -q,form a dipole separated by a distance d.A third charge Q is placed midway between these two charges.If the distance between q and -q is then doubled with the Q staying midway between the other two,what happens to the force on Q?

Accepted Answer

The force on charge Q due to the dipole (q, -q) can be described by the formula:

F = (1/4πε) [(q/r1^2 - q/r2^2) * d]

where ε is the permittivity of free space, r1 and r2 are the distances from Q to q and -q respectively, and d is the separation between q and -q.

When the distance between q and -q is doubled, the separation d in the above formula also doubles. Therefore, the force on Q becomes:

F' = (1/4πε) [(q/(2r1)^2 - q/(2r2)^2) * 2d]

Simplifying this expression, we get:

F' = (1/4πε) [(q/r1^2 - q/4r2^2) * 2d]

Notice that the second term in the bracket becomes smaller by a factor of 4, since the distance r2 is doubled. Therefore, the new force F' is:

F' = F/2

In other words, the force on Q is reduced by a factor of 2, or it quarters. Therefore, the correct answer is D.

Question 18

The combination of two separated point charges of opposite sign but equal magnitude is called an electric:

Accepted Answer

A dipole is created by two charges of opposite sign and equal magnitude separated by a distance. A monopole is a single point charge, a quadrapole is four charges with a specific arrangement, and a magnapole is not a recognized term in physics.

Question 19

If a conductor is in electrostatic equilibrium near an electrical charge:

Accepted Answer

When a conductor is in electrostatic equilibrium, the electric field inside the conductor is zero. This is because charges redistribute themselves on the surface of the conductor until the internal electric field cancels out.

Question 20

A thin uncharged conducting spherical shell has a charge q carefully placed at its center through a small hole in the shell.The charge q does not touch the shell.What is the charge on the outer surface of the shell?

Accepted Answer

Since the sphere is uncharged, the charge on the inner surface must be opposite to q to cancel it out. However, since the shell is uncharged, there cannot be any charge accumulation on the outer surface, so the charge on the outer surface is 0 (neutral).

Quiz 15: Electric Forces and Fields

We have an initially uncharged hollow metallic sphere with radius of 5.0 cm.I place a small object with a charge of +20 µC at the center of the sphere through a hole in the surface.Find the electric field present at a point 10 cm from the sphere's center.(k_e = 8.99 × 10⁹ N⋅m²/C²)

If a charge +Q is placed inside a hollow isolated conductor that is originally neutral and the charge does not touch that conductor at any time:

In the Millikan oil-drop experiment it was found that oil droplets:

The Millikan oil-drop experiment demonstrated that:

Relative distribution of charge density on the surface of a conducting solid depends on the

Two identical balls have the same amount of charge,but the charge on ball A is positive and the charge on ball B is negative.The balls are placed on a smooth,level,frictionless table whose top is an insulator.Which of the following is true?

We have a hollow metallic sphere with charge −5.20 µC and radius 5.40 cm.We insert a +10.4-µC charge at the center of the sphere through a hole in the surface.What charge now rests on the outer surface of the sphere?

A ping-pong ball covered with a conducting graphite coating has a mass of 5.4 × 10−³ kg and a charge of 3.8 µC.What electric field directed upward will exactly balance the weight of the ball? (g = 9.8 m/s²)

An initially uncharged hollow metallic sphere with radius of 5 cm has a small object with a charge of +15 µC carefully placed at the center of the sphere through a hole in the latter's surface.What charge resides inner surface of the sphere?

Two identical spheres each carry a charge of −82.0 µC.The spheres are separated by a distance of 2.00 m.What is the electric force between the spheres? (k_e = 8.99 × 10⁹ N·m²/C²)

The electric field at the surface of a positively charged conductor has a direction characterized by which of the following?

An initially uncharged hollow metallic sphere with radius of 6 cm has a small object with a charge of +14 µC carefully placed at the center of the sphere through a hole in the latter's surface.With the charge in place,what charge is now present on the outside surface of the sphere?

The electric field associated with a uniformly charged hollow metallic sphere is the greatest at:

At what point is the charge per unit area greatest on the surface of an irregularly shaped conducting solid?

Two point charges,one q and the other -q,form a dipole separated by a distance d.A third charge Q is placed midway between these two charges.If the distance between q and -q is then doubled with the Q staying midway between the other two,what happens to the force on Q?

The combination of two separated point charges of opposite sign but equal magnitude is called an electric:

If a conductor is in electrostatic equilibrium near an electrical charge:

A thin uncharged conducting spherical shell has a charge q carefully placed at its center through a small hole in the shell.The charge q does not touch the shell.What is the charge on the outer surface of the shell?

Quiz 15: Electric Forces and Fields

We have an initially uncharged hollow metallic sphere with radius of 5.0 cm.I place a small object with a charge of +20 µC at the center of the sphere through a hole in the surface.Find the electric field present at a point 10 cm from the sphere's center.(ke = 8.99 × 109 N⋅m2/C2) ​

If a charge +Q is placed inside a hollow isolated conductor that is originally neutral and the charge does not touch that conductor at any time:

In the Millikan oil-drop experiment it was found that oil droplets:

The Millikan oil-drop experiment demonstrated that:

Relative distribution of charge density on the surface of a conducting solid depends on the

Two identical balls have the same amount of charge,but the charge on ball A is positive and the charge on ball B is negative.The balls are placed on a smooth,level,frictionless table whose top is an insulator.Which of the following is true?

We have a hollow metallic sphere with charge −5.20 µC and radius 5.40 cm.We insert a +10.4-µC charge at the center of the sphere through a hole in the surface.What charge now rests on the outer surface of the sphere?​

A ping-pong ball covered with a conducting graphite coating has a mass of 5.4 × 10−3 kg and a charge of 3.8 µC.What electric field directed upward will exactly balance the weight of the ball? (g = 9.8 m/s2) ​

An initially uncharged hollow metallic sphere with radius of 5 cm has a small object with a charge of +15 µC carefully placed at the center of the sphere through a hole in the latter's surface.What charge resides inner surface of the sphere?

Two identical spheres each carry a charge of −82.0 µC.The spheres are separated by a distance of 2.00 m.What is the electric force between the spheres? (ke = 8.99 × 109 N·m2/C2) ​

The electric field at the surface of a positively charged conductor has a direction characterized by which of the following?

An initially uncharged hollow metallic sphere with radius of 6 cm has a small object with a charge of +14 µC carefully placed at the center of the sphere through a hole in the latter's surface.With the charge in place,what charge is now present on the outside surface of the sphere?​

The electric field associated with a uniformly charged hollow metallic sphere is the greatest at:

At what point is the charge per unit area greatest on the surface of an irregularly shaped conducting solid?

Two point charges,one ​q and the other -q,form a dipole separated by a distance d.A third charge Q is placed midway between these two charges.If the distance between q and -q is then doubled with the Q staying midway between the other two,what happens to the force on Q?

The combination of two separated point charges of opposite sign but equal magnitude is called an electric:

If a conductor is in electrostatic equilibrium near an electrical charge:

A thin uncharged conducting spherical shell has a charge q carefully placed at its center through a small hole in the shell.The charge q does not touch the shell.What is the charge on the outer surface of the shell?

We have an initially uncharged hollow metallic sphere with radius of 5.0 cm.I place a small object with a charge of +20 µC at the center of the sphere through a hole in the surface.Find the electric field present at a point 10 cm from the sphere's center.(k_e = 8.99 × 10⁹ N⋅m²/C²)

We have a hollow metallic sphere with charge −5.20 µC and radius 5.40 cm.We insert a +10.4-µC charge at the center of the sphere through a hole in the surface.What charge now rests on the outer surface of the sphere?

A ping-pong ball covered with a conducting graphite coating has a mass of 5.4 × 10−³ kg and a charge of 3.8 µC.What electric field directed upward will exactly balance the weight of the ball? (g = 9.8 m/s²)

Two identical spheres each carry a charge of −82.0 µC.The spheres are separated by a distance of 2.00 m.What is the electric force between the spheres? (k_e = 8.99 × 10⁹ N·m²/C²)

An initially uncharged hollow metallic sphere with radius of 6 cm has a small object with a charge of +14 µC carefully placed at the center of the sphere through a hole in the latter's surface.With the charge in place,what charge is now present on the outside surface of the sphere?

Two point charges,one q and the other -q,form a dipole separated by a distance d.A third charge Q is placed midway between these two charges.If the distance between q and -q is then doubled with the Q staying midway between the other two,what happens to the force on Q?