Electric Charges and Fields Quiz
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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?

    <p>Charge exists in discrete units</p> Signup and view all the answers

    What is the charge of a proton denoted as?

    <p>+e</p> Signup and view all the answers

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

    <p>One body gains charge and the other loses charge</p> Signup and view all the answers

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

    <p>Coulomb</p> Signup and view all the answers

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

    <p>Charge has magnitude but no direction</p> Signup and view all the answers

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

    <p>The leaves diverge.</p> Signup and view all the answers

    How does a neutral body become charged?

    <p>By losing electrons.</p> Signup and view all the answers

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

    <p>They lack free-moving electrons.</p> Signup and view all the answers

    Which of the following materials is considered a conductor?

    <p>Gold</p> 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?

    <p>The leaves diverge.</p> Signup and view all the answers

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

    <p>It becomes positively charged.</p> Signup and view all the answers

    How can a neutral body be charged positively?

    <p>By losing electrons.</p> Signup and view all the answers

    Which of the following materials is classified as a conductor?

    <p>Metal</p> Signup and view all the answers

    What characterizes semiconductors compared to conductors and insulators?

    <p>They offer intermediate resistance.</p> Signup and view all the answers

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

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

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

    <p>Their electrons are tightly bound.</p> Signup and view all the answers

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

    <p>The charge remains localized.</p> Signup and view all the answers

    What occurs when charge is put on an insulator?

    <p>The charge remains at the same location.</p> Signup and view all the answers

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

    <p>Electrons are transferred from the rod to the silk.</p> Signup and view all the answers

    What characterizes semiconductors in comparison to conductors and insulators?

    <p>They offer intermediate resistance to charge movement.</p> Signup and view all the answers

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

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

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

    <p>Metals do not retain charge.</p> Signup and view all the answers

    How do charged bodies typically acquire charge?

    <p>Through electron transfer.</p> Signup and view all the answers

    What is a characteristic of electric charge?

    <p>Charge can be both positive and negative.</p> Signup and view all the answers

    How are multiple point charges combined to determine total charge?

    <p>By adding all charges algebraically.</p> Signup and view all the answers

    What does the conservation of charge imply?

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

    Which statement reflects the quantization of charge?

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

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

    <p>One body gains charge while the other loses charge.</p> Signup and view all the answers

    What distinguishes mass from charge?

    <p>Mass and charge are both scalar quantities.</p> Signup and view all the answers

    What is the elementary charge associated with an electron?

    <p>-1.6 x 10^-19 C</p> Signup and view all the answers

    What is true about point charges in an electric field?

    <p>They are treated as having no size.</p> Signup and view all the answers

    What would happen in an isolated system concerning charges?

    <p>Charges can redistribute but total charge stays the same.</p> Signup and view all the answers

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

    <p>-1</p> Signup and view all the answers

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

    <p>The charge of an electron or proton</p> Signup and view all the answers

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

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

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

    <p>It remains zero</p> Signup and view all the answers

    What does the quantisation of charge imply?

    <p>Charge is always an integral multiple of <em>e</em></p> 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?

    <p>$(np - ne)e$</p> Signup and view all the answers

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

    <p>Michael Faraday</p> Signup and view all the answers

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

    <p>Charge appears continuous at the macroscopic level</p> Signup and view all the answers

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

    <p>Micro or milli coulombs</p> Signup and view all the answers

    What is the basic unit of charge represented by e?

    <p>The charge on a proton</p> 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?

    <p>Quantisation of charge</p> Signup and view all the answers

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

    <p>$6 imes 10^{18}$</p> Signup and view all the answers

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

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

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

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

    Which of the following units is equivalent to 1 µC?

    <p>$10^{-6} C$</p> Signup and view all the answers

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

    <p>Charge appears continuous.</p> Signup and view all the answers

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

    <p>Faraday</p> Signup and view all the answers

    What device did Coulomb invent to measure electric force?

    <p>Torsion balance</p> Signup and view all the answers

    What is the relationship established by Coulomb’s law?

    <p>Force is inversely proportional to the square of distance.</p> Signup and view all the answers

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

    <p>Electrostatic force constant.</p> Signup and view all the answers

    How did Coulomb determine the charge distribution on multiple spheres?

    <p>By putting them in contact with one another.</p> Signup and view all the answers

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

    <p>Each sphere acquires half of the total charge.</p> 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?

    <p>$F = 9 imes 10^9 N$</p> Signup and view all the answers

    What assumption is implicit in the concept of charge additivity?

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

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

    <p>Both macroscopic and subatomic levels.</p> Signup and view all the answers

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

    <p>Measuring gravitational force.</p> Signup and view all the answers

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

    <p>A definition for a unit of charge.</p> 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?

    <p>6.25 x 10⁹ seconds</p> Signup and view all the answers

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

    <p>1.34 x 10⁷ C</p> Signup and view all the answers

    What is Coulomb's law primarily concerned with?

    <p>The force between two point charges</p> Signup and view all the answers

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

    <p>A torsion balance</p> Signup and view all the answers

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

    <p>The distance between the charges</p> Signup and view all the answers

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

    <p>2.5 x 10²⁴ electrons</p> Signup and view all the answers

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

    <p>18 g</p> Signup and view all the answers

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

    <p>The magnitude of the force</p> Signup and view all the answers

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

    <p>Charges are evenly distributed when in contact.</p> Signup and view all the answers

    Which device did Coulomb invent to measure electrical forces?

    <p>Torsion balance</p> Signup and view all the answers

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

    <p>It is directly proportional to the product of the charges.</p> Signup and view all the answers

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

    <p>Charge is evenly distributed between the spheres.</p> Signup and view all the answers

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

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

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

    <p>It is defined through experimental evidence of forces.</p> 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?

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

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

    <p>It is applicable at both macroscopic and subatomic levels.</p> Signup and view all the answers

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

    <p>Cavendish</p> Signup and view all the answers

    What characteristic defines a torsion balance?

    <p>It is a sensitive device for measuring force.</p> 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?

    <p>6.25 x $10^{18}$</p> Signup and view all the answers

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

    <p>1.34 x $10^5$ C</p> Signup and view all the answers

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

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

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

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

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

    <p>A torsion balance.</p> Signup and view all the answers

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

    <p>2.5 x $10^{24}$</p> Signup and view all the answers

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

    <p>Force is directly proportional to the product of the charges.</p> 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?

    <p>The force doubles.</p> 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.

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