Question 1

To make an uncharged object have a negative charge we must:&#10;A) add some atoms&#10;B) remove some atoms&#10;C) add some electrons&#10;D) remove some electrons&#10;E) write down a negative sign

Accepted Answer

Adding electrons to an uncharged object increases its negative charge because electrons carry a negative charge.

Question 2

To make an uncharged object have a positive charge:&#10;A) remove some neutrons&#10;B) add some neutrons&#10;C) add some electrons&#10;D) remove some electrons&#10;E) heat it to cause a change of phase

Accepted Answer

Removing electrons from an object, which are negatively charged, will leave the object with a net positive charge because it will have more protons, which are positively charged, than electrons.

Question 3

An electrical insulator is a material:&#10;A) containing no electrons&#10;B) through which electrons do not flow easily&#10;C) which has more electrons than protons on its surface&#10;D) cannot be a pure chemical element&#10;E) must be a crystal

Accepted Answer

Electrical insulators are materials through which electrons do not flow easily, making them ideal for preventing unwanted electrical currents.

Question 4

A conductor is distinguished from an insulator with the same number of atoms by the number of:&#10;A) nearly free atoms&#10;B) electrons&#10;C) nearly free electrons&#10;D) protons&#10;E) molecules

Accepted Answer

Conductors differ from insulators in their number of nearly free electrons. These electrons are not bound to any particular atom and can move freely through the material, allowing it to conduct electricity. Insulators, on the other hand, have their electrons tightly bound to atoms, preventing free movement and thus conductivity.

Question 5

The leaves of a positively charged electroscope diverge more when an object is brought near the knob of the electroscope. The object must be:&#10;A) a conductor&#10;B) an insulator&#10;C) positively charged&#10;D) negatively charged&#10;E) uncharged

Accepted Answer

The object must be positively charged because like charges repel each other.

Question 6

Consider the following procedural steps:
(1) ground the electroscope
(2) remove the ground from the electroscope
(3) touch a charged rod to the electroscope
(4) bring a charged rod near, but not touching, the electroscope
(5) remove the charged rod
To charge an electroscope by induction, use the sequence:

A) 1, 4, 5, 2
B) 4, 1, 2, 5
C) 3, 1, 2, 5
D) 4, 1, 5, 2
E) 3, 5

Accepted Answer

To charge an electroscope by induction, bring a charged rod near it (4), ground the electroscope (1), remove the ground (2), and then remove the charged rod (5).

Question 7

A charged insulator can be discharged by passing it just above a flame. This is because the flame:&#10;A) warms it&#10;B) dries it&#10;C) contains carbon dioxide&#10;D) contains ions&#10;E) contains more rapidly moving atoms

Accepted Answer

The flame contains ions which can neutralize the charge on the insulator by providing charge carriers that can move to or from the insulator, thus discharging it.

Question 8

A small object has charge Q. Charge q is removed from it and placed on a second small object. The two objects are placed 1 m apart. For the force that each object exerts on the other to be a maximum. q should be:

A) 2Q
B) Q
C) Q/2
D) Q/4
E) 0

Accepted Answer

The force between two charges is given by Coulomb's law, $F = k \frac{|q_1 q_2|}{r^2}$, where $q_1$ and $q_2$ are the charges, $r$ is the distance between them, and $k$ is Coulomb's constant. To maximize the force, we need to maximize the product $|q_1 q_2|$. If the initial charge is $Q$ and $q$ is removed, then one object has charge $q$ and the other has charge $Q-q$. The product of the charges is $q(Q-q)$. To find the maximum value, we can take the derivative with respect to $q$ and set it to zero: $\frac{d}{dq}[q(Q-q)] = Q - 2q = 0$, solving for $q$ gives $q = Q/2$.

Deck 6: Coulombs Law