Electrostatics and Electric Fields Quiz
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Questions and Answers

What happens when two glass rods, rubbed with wool, are brought close to each other?

  • They attract each other.
  • They change color.
  • They do not interact at all.
  • They repel each other. (correct)

    • Which material does a plastic rod attract after being rubbed with fur?

  • Pith balls. (correct)
  • Another plastic rod.
  • A glass rod.
  • Silk cloth.

    • When a plastic rod rubbed with fur touches pith balls, what occurs?

  • The pith balls become neutral.
  • The pith balls gain a charge and repel each other. (correct)
  • The pith balls attract each other.
  • The pith balls stick to the rod.

    • What type of electric charge do glass and plastic rods acquire when rubbed?

    <p>They acquire either positive or negative charge.</p> Signup and view all the answers

    What is observed when a glass rod rubbed with silk touches another glass rod?

    <p>They repel each other.</p> Signup and view all the answers

    Which of the following materials does NOT attract a plastic rod?

    <p>Wood.</p> Signup and view all the answers

    After rubbing, how do two strands of wool behave when brought close to each other?

    <p>They repel each other.</p> Signup and view all the answers

    What type of experiment establishes the existence of electric charges?

    <p>Careful analyses of electrostatic behavior.</p> Signup and view all the answers

    What happens to the free electrons in sphere A when a positively charged rod is brought near it?

    <p>They are attracted towards the rod.</p> Signup and view all the answers

    After the positively charged rod is removed, what happens to the charges on the spheres?

    <p>The charges redistribute to their original neutral state.</p> Signup and view all the answers

    What type of charging process is observed when the spheres are separated while the rod is still held near sphere A?

    <p>Charging by induction</p> Signup and view all the answers

    What charge does the left surface of sphere A develop when the positively charged rod is close?

    <p>Negative charge</p> Signup and view all the answers

    What occurs to the insulative forces acting on the charges during the induction process?

    <p>They balance the attraction and repulsion forces.</p> Signup and view all the answers

    What is the net charge on each sphere after the glass rod is removed and the spheres are separated?

    <p>One sphere is negatively charged, and the other is positively charged.</p> Signup and view all the answers

    Why does charging by induction not cause the positively charged rod to lose any charge?

    <p>No physical contact is made with the spheres.</p> Signup and view all the answers

    What happens to the charges once the rod is removed and the spheres are sufficiently separated?

    <p>They redistribute uniformly over the surfaces of each sphere.</p> Signup and view all the answers

    What occurs when electrified rods are brought near light objects?

    <p>Opposite charges are induced on the near surfaces of the objects.</p> Signup and view all the answers

    What causes lighter particles, like bits of paper, to be attracted towards electrified rods?

    <p>The force of attraction outweighs the force of repulsion.</p> Signup and view all the answers

    How can a metallic sphere be charged positively without direct contact?

    <p>By bringing a negatively charged rod close to it.</p> Signup and view all the answers

    During the charging process described, what happens to the free electrons in the metallic sphere?

    <p>They pile up at the near end due to repulsion.</p> Signup and view all the answers

    What does the electric field E represent in the context of a system of charges?

    <p>The force on a charge without considering the charge's influence on the system.</p> Signup and view all the answers

    What happens when the metallic sphere is connected to the ground?

    <p>Electrons flow from the sphere to the ground.</p> Signup and view all the answers

    What ensures that the positive charge at the near end of the sphere is maintained after disconnecting from the ground?

    <p>The attractive force of the negative charges on the rod.</p> Signup and view all the answers

    How is the electric field E mathematically expressed based on the positions of the source charges?

    <p>E = 4πε_0 ∑ r^2i rˆi P</p> Signup and view all the answers

    In the described charging process, which statement is true after the rod is removed?

    <p>The positive charge spreads uniformly over the sphere.</p> Signup and view all the answers

    Why is the concept of an electric field considered convenient in electrostatics?

    <p>It characterizes the electric environment without measuring disturbance.</p> Signup and view all the answers

    What is the term used to describe the charging of the metallic sphere as a result of the negatively charged rod being brought near?

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

    What characteristic does the electric field possess regarding the unit positive test charge used to measure it?

    <p>It is defined independently of the test charge.</p> Signup and view all the answers

    In the context of electric fields, what is true about the vector nature of E?

    <p>Electric fields vary in direction and magnitude from point to point.</p> Signup and view all the answers

    What is the relationship between electric field and the measurable force on a charge?

    <p>Electric field is derived from the force acting on a unit charge.</p> Signup and view all the answers

    What does the term 'field' generally refer to in physics?

    <p>A variable quantity defined at every point in space.</p> Signup and view all the answers

    What does the use of Coulomb's law and the superposition principle imply in the context of electric fields?

    <p>They can be used to calculate total electric force from charges.</p> Signup and view all the answers

    What is the primary purpose of introducing the concept of the electric field?

    <p>To explain time-dependent electromagnetic phenomena and their effects.</p> Signup and view all the answers

    How does the motion of charge q1 affect charge q2 according to the electric field concept?

    <p>There is a time delay in the effects due to the finite speed of light.</p> Signup and view all the answers

    What is the relationship between electric and magnetic fields and their detection?

    <p>They can be detected only through their effects on electric charges.</p> Signup and view all the answers

    What happens when a source of time-dependent electromagnetic fields is switched off?

    <p>They continue to propagate and can transport energy.</p> Signup and view all the answers

    Why is the electric field concept considered to have independent dynamics?

    <p>It evolves according to its own laws and influences forces on other charges.</p> Signup and view all the answers

    What force does the electron experience in an upward electric field?

    <p>A downward force equal to its charge multiplied by the electric field magnitude.</p> Signup and view all the answers

    How would the motion of a proton differ from that of an electron in the same electric field?

    <p>The proton would experience an upward force instead of downward.</p> Signup and view all the answers

    Who first introduced the concept of the electric field?

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

    What determines the amount of water flowing through a ring in a stream?

    <p>The orientation of the ring relative to the flow</p> Signup and view all the answers

    What represents the direction of a planar area vector?

    <p>The outward normal of the surface</p> Signup and view all the answers

    How is the direction of the area element vector determined for a closed surface?

    <p>It follows a convention of being outward</p> Signup and view all the answers

    What is the equation that defines electric flux through an area element ΔS?

    <p>Δφ = E ΔS cosθ</p> Signup and view all the answers

    In the context of electric flux, what does the angle θ represent?

    <p>The angle between the area vector and the electric field</p> Signup and view all the answers

    What occurs when dividing a curved surface into small area elements?

    <p>Each area element can be treated as planar</p> Signup and view all the answers

    What is a common challenge when identifying the direction of an area element vector?

    <p>There are multiple normals that can point in two directions</p> Signup and view all the answers

    Which statement correctly describes the area element vector ΔS for a closed surface?

    <p>It equals ΔS n̂, where n̂ points outward</p> Signup and view all the answers

    Study Notes

    Electrostatics and Electric Fields

    • Charges Repel/Attract: Different materials (glass, plastic, wool, silk) rubbed together develop electric charges. Like charges repel (e.g., glass rod rubbed with wool repels another glass rod rubbed with wool). Unlike charges attract (e.g., glass rod rubbed with wool attracts a plastic rod rubbed with fur).

    • Charging by Induction: A charged object brought near an uncharged conductor induces charges in the conductor. The charges on the conductor are separated; the side nearest the charged object acquires the opposite charge, and the further side acquires the same charge as the inducing object. This charge separation allows charging without direct contact.

    • The conductor is connected to ground. Electrons leave to balance the charge. The connection is removed. The object now holds opposite charge to the initial charged object.

    • The charged object is removed and the induced charge distributes evenly.

    • Electric Field: Describes the electrical environment of a system of charged particles. An electric field specifies the force on a unit positive test charge at a given point in space.

    • It's a vector quantity, and its properties are determined by the charge distribution, and it's independent of the test charge.

    • The magnitude depends on the distance between the charges.

    • The notion of an electric field is essential for understanding time-dependent electromagnetic phenomena (e.g., force between moving charges). The field allows us to account for delays in the interaction.

    • Electric Flux: Describes the extent to which electric field lines pass through a surface. Measured by calculating the product of the electric field strength and the projected area of the surface perpendicular to the field.

    • The direction of the associated area vector is along the outward normal for a closed surface.

    • Δφ = E • ΔS = E ΔS cosθ (product of the electric field strength (E), projected area (ΔS) and the cosine of the angle (θ) between the field and the surface normal)

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    Description

    Test your understanding of electrostatics and electric fields with this quiz. Explore concepts such as charge interaction, charging by induction, and the behavior of electric fields. Perfect for students studying physics at any level.

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