Question 1

How does a permanent magnet work, i.e., what is the explanation of its magnetic effects?

Accepted Answer

The magnetic effects of a permanent magnet are due to the alignment of electrons' spins and their orbital motion around atoms, which creates a net magnetic field.

Question 2

The force between two bar magnets cannot be due to gravity, because

Accepted Answer

The force between magnets is much stronger than gravitational force and can be both attractive and repulsive, unlike gravity which is always attractive.

Question 3

A charged particle is placed at rest in the middle of a vacuum chamber, an enclosure that has been emptied of all matter. Consider some point X near a particular corner of the chamber. Neglecting all influences other than the charged particle, what can be said regarding electric fields and magnetic fields at point X?

Accepted Answer

A stationary charged particle creates an electric field but no magnetic field, as magnetic fields are produced by moving charges.

Question 4

A changing magnetic field creates an electric field. This is one way of stating

Accepted Answer

Faraday's law of electromagnetic induction states that a changing magnetic field induces an electric field.

Question 5

What form of energy do electrons have when they're at rest on the negative terminal of an isolated (not connected to an electrical circuit) batters?

Accepted Answer

Electrons at rest on the negative terminal of a battery have electrical potential energy due to their position in an electric field.

Question 6

Suppose you charge two transparencies by rubbing and then hold them near each other without letting them touch, and shake both of them back and forth. Regarding the electric and magnetic forces they exert on each other,

Accepted Answer

When charged objects are moved, they create changing electric fields, which can induce magnetic fields, resulting in both electric and magnetic forces being exerted on each other.

Question 7

The planetary model of the atom is a more detailed, or sophisticated, model than the simpler Greek model of the atom. The planetary model is useful because, unlike the Greek model, it can explain

Accepted Answer

The answer of The planetary model of the atom is...

Question 8

Object A has an electric charge that is 10 times larger than the charge on object B. When placed near each other, how does the force by A on B compare with the force by B on A?

Accepted Answer

According to Newton's third law of motion, the force exerted by object A on object B is equal in magnitude and opposite in direction to the force exerted by object B on object A, regardless of the difference in their charges.

Question 9

In a single electric cord, such as a cord that connects a wall socket with an electric light,

Accepted Answer

In an electric cord, there are typically two wires: one carries electrons (current) into the light bulb, and the other carries electrons back out, completing the circuit.

Question 10

Suppose you electrically charge a transparency by rubbing it, and then hang the transparency, at rest, by a string in the center of a room. Except for the transparency and string, the room is totally evacuated of all matter. Neglecting any influences from outside the room, what kinds of fields would then be found at places inside the room but away from the transparency-- for instance, at a point near a corner of the room?

Accepted Answer

The charged transparency creates an electric field in the room, even in the absence of other materials.

Question 11

The atomic nucleus contains

Accepted Answer

The atomic nucleus contains protons and neutrons. Electrons are located outside the nucleus in the electron cloud.

Question 12

Suppose you released a single proton from rest at some point X in an electric field, and that you then released a single electron from rest at the same point X. How would the motions of the proton and electron compare, just after their release from rest?

Accepted Answer

The proton and electron have opposite charges, so they will move in opposite directions in an electric field. The electron, having much less mass than the proton, will accelerate faster and thus move faster.

Question 13

What is the explanation of Earth's magnetism?

Accepted Answer

Earth's magnetism is primarily caused by the movement of electrically charged materials, such as molten iron and nickel, within its liquid outer core. This movement generates electric currents, which in turn produce magnetic fields, creating a geodynamo effect that sustains Earth's magnetic field.

Question 14

An "ion" is

Accepted Answer

An ion is an atom or molecule that has gained or lost one or more electrons, resulting in a net electrical charge.

Question 15

If you rub two transparency sheets with tissue and then hold the two transparency sheets at rest a short distance apart, they will then exert

Accepted Answer

Rubbing the transparency sheets with tissue transfers electrons, charging them with the same type of charge, causing them to repel each other due to electric forces.

Question 16

What should be the resistance of a light bulb in order for it to draw a 2 amp current when plugged into a 120- volt outlet?

Accepted Answer

Using Ohm's Law (V = IR), the resistance (R) can be calculated as R = V/I = 120 volts / 2 amps = 60 ohms.

Question 17

A neutral atom loses one of its electrons. It is then

Accepted Answer

When a neutral atom loses an electron, it has more protons than electrons, resulting in a positive charge, making it a positive ion.

Question 18

What physics principle can be demonstrated by rubbing two transparency sheets with tissue paper and then holding them near each other?

Accepted Answer

Rubbing transparency sheets with tissue paper transfers electrons, creating static electricity. When held near each other, the sheets exhibit electric forces due to their charged states.

Question 19

An electromagnetic field

Accepted Answer

An electromagnetic field is a region where a charge experiences a force, and it can also exist in a vacuum, as electromagnetic waves (like light) can propagate through empty space.

Question 20

A blow dryer with a resistance of 6 ohms is plugged into a 60- volt battery. How much current does it draw?

Accepted Answer

Using Ohm's Law (V = IR), the current (I) can be calculated as I = V/R = 60 volts / 6 ohms = 10 amps.

Quiz 8: Light and Electromagnetism