Electric Charges and Fields Quiz

Questions and Answers

What are the two types of electric charges?

Negative and Zero

Positive and Negativ (correct)

Negative and Neutral

Positive and Neutral

How does the total charge of a system with multiple charges get calculated?

By adding the magnitudes with proper signs (correct)

By multiplying the charges together

By taking the maximum charge value

By averaging the charges

What is the principle of conservation of charge?

Charge can only exist in multiples of five

Charge can be created through heating

Total charge in an isolated system remains constant (correct)

Charge can be destroyed in particle collisions

What does the quantisation of charge indicate?

Charge exists in discrete units Signup and view all the answers

What is the charge of a proton denoted as?

+e Signup and view all the answers

What happens to the charge when two bodies are rubbed together?

One body gains charge and the other loses charge Signup and view all the answers

What unit is used to express electric charge in the International System of Units (SI)?

Coulomb Signup and view all the answers

What is charge compared to mass in terms of its properties?

Charge has magnitude but no direction Signup and view all the answers

What happens to the gold leaves of an electroscope when a charged object touches the metal knob?

The leaves diverge. Signup and view all the answers

How does a neutral body become charged?

By losing electrons. Signup and view all the answers

Why do insulators hold charge in one place instead of distributing it?

They lack free-moving electrons. Signup and view all the answers

Which of the following materials is considered a conductor?

Gold Signup and view all the answers

What happens to the gold leaves in a gold-leaf electroscope when a charged object touches its metal knob?

The leaves diverge. Signup and view all the answers

What type of charge does a glass rod acquire when rubbed with silk?

It becomes positively charged. Signup and view all the answers

How can a neutral body be charged positively?

By losing electrons. Signup and view all the answers

Which of the following materials is classified as a conductor?

Metal Signup and view all the answers

What characterizes semiconductors compared to conductors and insulators?

They offer intermediate resistance. Signup and view all the answers

What is the role of electrons in charging a solid material?

Electrons can be transferred from one object to another. Signup and view all the answers

What is the primary reason why insulators do not conduct electricity well?

Their electrons are tightly bound. Signup and view all the answers

When a charged insulator is touched, what is the expected outcome?

The charge remains localized. Signup and view all the answers

What occurs when charge is put on an insulator?

The charge remains at the same location. Signup and view all the answers

Which process is responsible for charging a glass rod when rubbed with silk?

Electrons are transferred from the rod to the silk. Signup and view all the answers

What characterizes semiconductors in comparison to conductors and insulators?

They offer intermediate resistance to charge movement. Signup and view all the answers

What is the role of the gold-leaf electroscope in detecting charges?

It indicates the amount of charge based on leaf divergence. Signup and view all the answers

Why does a metal object not become electrified when combing dry hair?

Metals do not retain charge. Signup and view all the answers

How do charged bodies typically acquire charge?

Through electron transfer. Signup and view all the answers

What is a characteristic of electric charge?

Charge can be both positive and negative. Signup and view all the answers

How are multiple point charges combined to determine total charge?

By adding all charges algebraically. Signup and view all the answers

What does the conservation of charge imply?

The net charge of an isolated system is always conserved. Signup and view all the answers

Which statement reflects the quantization of charge?

Charge is composed of integral multiples of a basic unit. Signup and view all the answers

What happens to the charge of two bodies when they are rubbed together?

One body gains charge while the other loses charge. Signup and view all the answers

What distinguishes mass from charge?

Mass and charge are both scalar quantities. Signup and view all the answers

What is the elementary charge associated with an electron?

-1.6 x 10^-19 C Signup and view all the answers

What is true about point charges in an electric field?

They are treated as having no size. Signup and view all the answers

What would happen in an isolated system concerning charges?

Charges can redistribute but total charge stays the same. Signup and view all the answers

What is the sum of charges +1, +2, -3, +4, and -5?

-1 Signup and view all the answers

What defines the basic unit of charge, denoted by e?

The charge of an electron or proton Signup and view all the answers

What is the value of the basic unit of charge in the International System of Units?

$1.602192 × 10^{-19}$ C Signup and view all the answers

What happens to the total charge during the creation of a proton and an electron from a neutron?

It remains zero Signup and view all the answers

What does the quantisation of charge imply?

Charge is always an integral multiple of e Signup and view all the answers

According to the quantisation of charge, the total charge on a body containing ne electrons and np protons is given by which equation?

$(np - ne)e$ Signup and view all the answers

Who first suggested the concept of quantisation of charge through the laws of electrolysis?

Michael Faraday Signup and view all the answers

What does the term 'grainy nature of charge' refer to?

Charge appears continuous at the macroscopic level Signup and view all the answers

At the macroscopic level, charges are typically measured in which units?

Micro or milli coulombs Signup and view all the answers

What is the basic unit of charge represented by e?

The charge on a proton Signup and view all the answers

What is the term used to describe that electric charge is always an integral multiple of the basic charge unit?

Quantisation of charge Signup and view all the answers

How many electrons are roughly contained in a charge of -1 C?

$6 imes 10^{18}$ Signup and view all the answers

What is the value of the elementary charge e in coulombs?

$1.602 imes 10^{-19} C$ Signup and view all the answers

What is the relationship of total charge to electrons and protons in a body?

Total charge = $(n_e - n_p)e$ Signup and view all the answers

Which of the following units is equivalent to 1 µC?

$10^{-6} C$ Signup and view all the answers

What is the common perception of charge at the macroscopic level compared to its quantized nature?

Charge appears continuous. Signup and view all the answers

Who first suggested the quantisation of charge based on experimental laws?

Faraday Signup and view all the answers

What device did Coulomb invent to measure electric force?

Torsion balance Signup and view all the answers

What is the relationship established by Coulomb’s law?

Force is inversely proportional to the square of distance. Signup and view all the answers

What does the variable 'k' in Coulomb's law represent?

Electrostatic force constant. Signup and view all the answers

How did Coulomb determine the charge distribution on multiple spheres?

By putting them in contact with one another. Signup and view all the answers

What happens to charges when two identical uncharged spheres are put in contact?

Each sphere acquires half of the total charge. Signup and view all the answers

What is the force experienced by a charge of 1 C placed 1 m from another charge of the same magnitude in vacuum?

$F = 9 imes 10^9 N$ Signup and view all the answers

What assumption is implicit in the concept of charge additivity?

Two charges can combine to give a total charge. Signup and view all the answers

At what scale was Coulomb's law established, according to the text?

Both macroscopic and subatomic levels. Signup and view all the answers

What was one of the uses of the torsion balance besides measuring electric force?

Measuring gravitational force. Signup and view all the answers

What can Coulomb's law provide in terms of defining charge?

A definition for a unit of charge. Signup and view all the answers

How many seconds are required to accumulate a charge of 1 C if 10⁹ electrons move out every second?

6.25 x 10⁹ seconds Signup and view all the answers

What is the total charge present in a cup of water assumed to weigh 250 g?

1.34 x 10⁷ C Signup and view all the answers

What is Coulomb's law primarily concerned with?

The force between two point charges Signup and view all the answers

What device did Coulomb use to measure the force between charged spheres?

A torsion balance Signup and view all the answers

In Coulomb's law formula, what does the variable 'r' represent?

The distance between the charges Signup and view all the answers

How many electrons are there in one cubic centimeter of copper?

2.5 x 10²⁴ electrons Signup and view all the answers

What is the molecular mass of water used to find the number of molecules in one cup?

18 g Signup and view all the answers

What does the twist of the torsion wire indicate when measuring the force between charged spheres?

The magnitude of the force Signup and view all the answers

What principle did Coulomb use to find the charges on the metallic spheres?

Charges are evenly distributed when in contact. Signup and view all the answers

Which device did Coulomb invent to measure electrical forces?

Torsion balance Signup and view all the answers

What does Coulomb's law express about the force between two charges?

It is directly proportional to the product of the charges. Signup and view all the answers

What happens when two identical charged spheres are placed in contact?

Charge is evenly distributed between the spheres. Signup and view all the answers

What is the value of the constant k in Coulomb's law in SI units?

9 x 10^9 Nm²/C² Signup and view all the answers

What can be inferred about Coulomb's law concerning the magnitude of charge?

It is defined through experimental evidence of forces. Signup and view all the answers

What is the nature of the force experienced by two identical charges placed 1 meter apart in a vacuum?

The force is repulsive and equal to 9 x 10^9 N. Signup and view all the answers

Which of the following statements about Coulomb's law is correct?

It is applicable at both macroscopic and subatomic levels. Signup and view all the answers

Which scientist's work anticipated Coulomb's law before he published it?

Cavendish Signup and view all the answers

What characteristic defines a torsion balance?

It is a sensitive device for measuring force. Signup and view all the answers

How many electrons are equivalent to a total charge of 1 C, given that one electron has a charge of approximately $1.6 imes 10^{-19}$ C?

6.25 x $10^{18}$ Signup and view all the answers

What is the total charge contained in a cup of water with a mass of 250 g?

1.34 x $10^5$ C Signup and view all the answers

What does Coulomb's law state about the force between two point charges?

It varies inversely with the square of the distance between the charges. Signup and view all the answers

Why are charged bodies treated as point charges in some scenarios?

Because the size of the charged bodies is negligible compared to the distance separating them. Signup and view all the answers

What method did Coulomb use to measure the force between charged bodies?

A torsion balance. Signup and view all the answers

What is the approximate number of electrons in one cubic centimeter of copper?

2.5 x $10^{24}$ Signup and view all the answers

What relationship does Coulomb's law express regarding force and charge magnitudes?

Force is directly proportional to the product of the charges. Signup and view all the answers

If one charge is doubled while the distance remains the same, what happens to the force between the two charges according to Coulomb's law?

The force doubles. Signup and view all the answers

Study Notes

Electric Charges and Detection

The gold-leaf electroscope is an apparatus that detects charge by using a vertical metal rod with two thin gold leaves.
When a charged object touches the metal knob, charge flows to the leaves causing them to diverge; the degree of divergence indicates the amount of charge.
Matter is typically electrically neutral, but contains balanced charges at the atomic and molecular level.
Electric forces underpin various physical interactions, such as adhesive forces and surface tension.

Charging Mechanism

Electrifying a neutral body involves adding or removing charge; charged bodies present an excess or deficit of charge.
In solids, loosely bound electrons can be transferred to charge bodies positively (by losing electrons) or negatively (by gaining electrons).
Rubbing a glass rod with silk transfers electrons from the rod to the silk, resulting in a positively charged rod and a negatively charged silk without creating new charges.

Conductors and Insulators

Conductors allow the easy passage of electricity; examples include metals and the human body.
Insulators resist electricity flow; non-metals like glass, porcelain, plastic, and wood fall into this category.
Charges in conductors distribute across their surface, while those in insulators remain in one place.
Semiconductors have intermediate properties between conductors and insulators.

Basic Properties of Electric Charge

Two types of electric charges exist: positive and negative, often cancelling each other's effects.
In point charge approximation, the charge is considered to be concentrated at one point in space.

Additivity and Conservation of Charge

The total charge in a system can be found by algebraically adding individual charges (q₁ and q₂).
Charge is conserved; when bodies are charged through electron transfer, there’s no creation or destruction of total charged particles.
Charges may redistribute in an isolated system but the total remains constant.

Quantisation of Charge

Charge exists in discrete units, primarily associated with electrons and protons; charge on an electron is -e, while that on a proton is +e.
The quantisation of charge was experimentally verified by Robert Millikan in 1912.
The basic unit of charge, denoted as e, is 1.602192 × 10⁻¹⁹ C (Coulomb).

Practical Implications of Charge

The charge of 1 C is substantial; for example, it takes about 200 years to acquire this charge if 10⁹ electrons move out of a body every second.
A cubic centimeter of copper contains approximately 2.5 × 10²⁴ electrons.

Coulomb’s Law

Coulomb's law quantitatively describes the force between two point charges, influenced by the charges' magnitudes and the distance separating them.
The formula for the force (F) between two point charges q₁ and q₂ separated by distance r is:

$F = k \frac{q₁ q₂}{r²}$
Coulomb used a torsion balance to measure the force between charged metallic spheres, observing varying forces based on distance and charge magnitudes.### Charge Accumulation and Time Calculation
Accumulating a charge of 1 coulomb (C) from a body releasing 10^9 electrons per second takes approximately 200 years.
Charge of 10^9 electrons: (1.6 \times 10^{-19} \times 10^9 = 1.6 \times 10^{-10} C) per second.
A cubic centimeter of copper contains roughly (2.5 \times 10^{24}) electrons.

Analysis of Water Charges

A cup of water (250 g) consists of about (1.34 \times 10^{5} C) of total charge, combining positive and negative charges.
The molecular mass of water is 18 g, and one mole contains (6.02 \times 10^{23}) molecules.

Coulomb's Law Fundamentals

Coulomb's Law states that the force (F) between two point charges (q_1) and (q_2) separated by distance (r) is given by: [ F = k \frac{|q_1 q_2|}{r^2} ]
(k) is a constant, approximately (9 \times 10^{9} , \text{Nm}^2/\text{C}^2) in SI units.
If (q_1 q_2 = 1C) at (r = 1m), the force (F) equals (9 \times 10^{9} N).

Coulomb's Methodology

Coulomb used a torsion balance to measure electric forces between metallic spheres.
Charges on the spheres were initially unknown; he established a method of charge division by contact with identical spheres.
He varied distances and charges systematically to derive the inverse square law.

Characteristics of Coulomb's Law

Established both at macroscopic (normal sizes) and subatomic levels (approximately (r \sim 10^{-15} m)).
Implicitly assumes charge additivity and conservation principles.

Historical Context of Coulomb

Charles Augustin de Coulomb (1736-1806), a French physicist, made significant advancements in electrostatics after retiring to conduct research in Paris.
His torsion balance, employed to measure electrical attraction and repulsion, significantly contributed to the formulation of Coulomb's law.
Previous anticipations of the inverse square law existed from scientists like Priestley and Cavendish, though Cavendish's results were not published.

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Description

Test your understanding of electric charges and fields with this quiz focusing on the gold-leaf electroscope and charge acquisition in materials. Explore the fundamental principles of static electricity and the behavior of charged bodies. Perfect for students studying electricity in physics.