Question 1

An electron situated near another electron would feel

Accepted Answer

Electrons are negatively charged particles and like charges repel each other. The repulsive force between them is an electrical force.

Question 2

After a glass rod is rubbed with a nylon cloth

Accepted Answer

When two materials are rubbed together, they exchange electrons. In this case, the glass rod has a stronger affinity for electrons than the nylon cloth, so it pulls electrons from the cloth onto itself. This leaves the rod with a negative charge (since it now has more electrons than protons) and the cloth with a positive charge (since it now has fewer electrons than protons). Therefore, the correct answer is B.

Question 3

The charge of a proton is due to

Accepted Answer

While physicists are not yet entirely sure why protons and other subatomic particles have electric charge, they do recognize charge as a fundamental property of the proton. It is not due to rapid spinning, periodic pulsations, or high density.

Question 4

A negatively charged rod is brought close to an uncharged electroscope. While the rod is close one's finger touches the far side of the metal ball on the electroscope. After the charged rod has been removed the finger is removed. The electroscope is

Accepted Answer

The answer of A negatively charged rod is brought close...

Question 5

Compared to the magnitude of the charge on a proton, the magnitude of the electrical charge carried by an electron is

Accepted Answer

The magnitude of the electrical charge carried by an electron is exactly the same as that of a proton, but they have opposite signs.

Question 6

A typical, neutrally charged atom has

Accepted Answer

A typical, neutrally charged atom has an equal number of protons and electrons. This is because the protons, which are positively charged, and electrons, which are negatively charged, cancel each other out and create a neutral charge. Option B is incorrect because most atoms have neutrons in the nucleus, but the number can vary depending on the element. Option C is incorrect because if an atom had more protons than electrons, it would have a positive charge. Option D is incorrect because neutrons do not have a charge, so they do not contribute to the overall charge of an atom. Option E is incorrect because some atoms, such as hydrogen, do not have any neutrons.

Question 7

Two equal positive charges are near each other. If we increase the amount of charge on just one of them, then

Accepted Answer

The electric field strength at a point is directly proportional to the source charge. Increasing the charge on one of them increases the electric field at the position of the other (smaller) charge.

Question 8

Our model for explaining the electrical interaction between charged objects

Accepted Answer

The model being described is one that postulates the existence of electric fields surrounding charged objects, and does not depend on high speeds, three kinds of charge, or the mass of the objects.

Question 9

A rubber rod is rubbed with fur, so that the fur becomes positive. The rod is then used to charge an electroscope. The charge on the electroscope will be

Accepted Answer

When a positively charged rod is brought near an object, it induces a negative charge on the surface of the object closest to the rod and a positive charge on the opposite side. This causes a separation of charges within the object, resulting in a temporary induced charge. In the case of an electroscope, the positively charged rod will induce a negative charge on the metal leaves of the electroscope, causing them to repel each other and indicating a positive charge. Therefore, the correct answer is D, positive if charged by induction.

Question 10

A 10 µC charge is at the origin. A -15 µC charge is on the x-axis 10 cm to the right of the origin. At what point other than at infinity can a 1 µC charge be placed so that there will be no net electrostatic force on it?

Accepted Answer

The 1 µC charge can be placed on the x-axis to the left of the positive charge where the forces due to the 10 µC and -15 µC charges balance each other.

Question 11

The electric field created by a moving negative charge

Accepted Answer

The electric field created by any charge, including a moving negative charge, points radially towards the charge if it is negative. This is because electric field lines originate from positive charges and terminate on negative charges, indicating the direction of the force that a positive test charge would experience in the presence of the electric field.

Question 12

The electrical force between any two charged objects is

Accepted Answer

The electrical force between two charged objects is dependent on the sign of the charge on each object. Objects with opposite charges are attracted to each other, while objects with the same charge are repelled.

Question 13

Comparing the electrostatic force and the gravitational force we can say that

Accepted Answer

Both electrostatic and gravitational forces have the same dependence on distance, following the inverse square law. However, the electrostatic force can be both attractive and repulsive, while the gravitational force is only attractive. Additionally, the electrostatic force is stronger than gravitational force as it is proportional to the square of the charge, while gravitational force is proportional to the mass only.

Question 14

A positively charged rod is brought close to an uncharged electroscope. While the rod is close, one's finger touches the far side of the metal ball on the electroscope. The finger is removed and then the rod is taken away. The electroscope is

Accepted Answer

When the positively charged rod is brought close, it induces a negative charge on the side of the electroscope near the rod and a positive charge on the far side. Touching the far side allows electrons to flow from the ground (through the finger) to neutralize the positive charge. When the finger is removed and then the rod is taken away, the electroscope retains a net negative charge.

Question 15

A metallic object has a net charge on it. For steady state conditions, the excess charge is

Accepted Answer

For steady state conditions, the excess charge will distribute itself so that it resides entirely on the surface of the object. This is due to the fact that excess charge will always repel other excess charge, and will therefore move as far away from itself as possible. As a result, any excess charge inside the object will experience a net force that drives it to the surface, where it can spread out and minimize its potential energy.

Question 16

The electrical force between two charged objects depends on

Accepted Answer

The electrical force between two charged objects depends on the product of the net charge on each of the two objects. This is known as Coulomb's Law and describes how the force between two charged objects varies with distance and the magnitude of the charges.

Question 17

Consider a proton and an electron placed near one another with no other objects close by. They would

Accepted Answer

Protons and electrons have opposite charges, so they attract each other via the electromagnetic force. Thus, they accelerate toward each other.

Question 18

If the potential at point A is one volt it means that

Accepted Answer

The potential at point A is one volt means that a charge at A has potential energy one joule for each coulomb of charge. Therefore, option A is the correct choice. Option B and C are incorrect as they do not necessarily follow from the given information. Option D is also incorrect as there is no mention of a battery present.

Question 19

A strip of fur is rubbed against a hard rubber rod. The rod thereby acquires a negative charge because

Accepted Answer

When the fur is rubbed against the rubber rod, electrons are transferred from the fur to the rod. This results in an excess of negative charge on the rod, causing it to become negatively charged.

Question 20

If the distance between two spherical charged objects decreases by a factor of two, then the electrical force between the objects

Accepted Answer

According to Coulomb's law, the electrical force between two charged objects is inversely proportional to the square of the distance between them. Therefore, if the distance between two spherical charged objects decreases by a factor of two, then the square of that distance decreases by a factor of four. This means that the electrical force between the objects increases by a factor of four, as the force is inversely proportional to the square of the distance.

Quiz 12: Electrostatic Phenomena