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Questions and Answers

What is the name given to the phenomenon that causes a spark or crackle when we take off our synthetic clothes?

Electric discharge

What is the other common example of electric discharge mentioned in the text?

Lightning

What does the term “Static” mean in the context of electrostatics?

Anything that does not move or change with time

What is the name of the Greek word from which the term “electricity” is derived?

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

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

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

What happens when a glass rod rubbed with wool is brought close to a piece of silk cloth?

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

The property that differentiates the two kinds of charges is called the polarity of charge.

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

What happens when an electrified glass rod is brought in contact with the silk cloth with which it was rubbed?

<p>They no longer attract or repel each other</p> Signup and view all the answers

Who was the American scientist who named charges as positive and negative?

<p>Benjamin Franklin</p> Signup and view all the answers

What is the name of the simple apparatus used to detect charge on a body?

<p>Gold-leaf electroscope</p> Signup and view all the answers

The degree of divergence of the gold leaves in an electroscope is an indicator of the amount of charge on the body.

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

Why do material bodies acquire charge?

<p>Due to the imbalance of charges</p> Signup and view all the answers

Forces that hold molecules together, forces that hold atoms together in a solid, the adhesive force of glue, forces associated with surface tension, all are basically electrical in nature.

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

What is the essential process for electrifying a neutral body?

<p>Adding or removing one kind of charge</p> Signup and view all the answers

In solids, electrons are the charges that are transferred from one body to another.

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

What happens when a body loses some of its electrons?

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

What happens when a body gains electrons?

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

Are new charges created during the process of rubbing?

<p>No</p> Signup and view all the answers

The number of electrons transferred during rubbing is a significant fraction of the total number of electrons in the material body.

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

What are substances that readily allow the passage of electricity through them called?

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

What are substances that offer high resistance to the passage of electricity through them called?

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

Metals, human and animal bodies, and earth are examples of conductors.

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

Glass, porcelain, plastic, nylon, and wood offer high resistance to the passage of electricity through them.

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

When some charge is transferred to a conductor, it stays at the same place.

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

When some charge is put on an insulator, it gets distributed over the entire surface.

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

What happens to the charges on a metal object that leaks through our body to the ground?

<p>They leak through our body to the ground</p> Signup and view all the answers

A metal rod with a wooden or plastic handle, when rubbed, will show signs of charging.

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

If the sizes of charged bodies are very small compared to the distances between them, we often treat them as what?

<p>Point charges</p> Signup and view all the answers

What is the total charge of a system containing charges of +1, +2, -3, +4, and -5, in some arbitrary unit?

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

When bodies are charged by rubbing, new charges are created.

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

Charges are either transferred or destroyed in the process of rubbing.

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

If a system consists of many charged bodies, what is always conserved?

<p>The total charge of the isolated system</p> Signup and view all the answers

It is possible to create or destroy net charge carried by an isolated system.

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

All free charges are integral multiples of a basic unit of charge denoted by e.

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

What is the charge on an electron conventionally taken to be?

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

What is the charge on a proton conventionally taken to be?

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

Charge can be both positive and negative.

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

The SI unit of charge is the coulomb (C).

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

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

<p>Approximately 6 x 10^18</p> Signup and view all the answers

In electrostatics, charges of this large magnitude (1C) are commonly encountered.

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

If the protons and electrons are the only basic charges in the universe, all the observable charges must be integral multiples of e.

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

The grainy nature of the charge is always visible at the macroscopic level.

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

What is Coulomb's law a quantitative statement about?

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

Coulomb's law is valid only for charges that are much smaller than the distance separating them.

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

What is the name of the instrument used by Coulomb to measure the force between two charged spheres?

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

The force between two point charges is directly proportional to the distance between the charges.

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

The force between two point charges is directly proportional to the product of the magnitudes of the two charges.

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

Coulomb's law was established by conducting experiments at subatomic level.

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

What does the choice of the constant k in Coulomb's law determine?

<p>The size of the unit of charge</p> Signup and view all the answers

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

<p>Approximately 9 x 10^9 Nm^2/C^2</p> Signup and view all the answers

What is 1 Coulomb equivalent to in terms of force?

<p>It is the charge that when placed at a distance of 1 meter from another charge of the same magnitude in vacuum, experiences a force of repulsion of magnitude 9 x 10^9 Newtons.</p> Signup and view all the answers

Coulomb's law only applies to charges in vacuum.

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

The force between two point charges does not depend on the medium in which they are placed.

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

What does the term “permittivity” of free space mean?

<p>It is the ability of a medium to allow electric field lines to pass through it</p> Signup and view all the answers

The permittivity of free space is denoted by Ɛ₀.

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

What is the value of Ɛ₀ in SI units?

<p>8.854 x 10^-12 C^2N^-1m^-2</p> Signup and view all the answers

Force is a vector quantity.

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

The charges add up like real numbers or scalars like the mass of a body.

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

Mass and charge are similar to each other in terms of magnitude and direction.

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

Coulomb's law agrees with Newton's third law.

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

What is the key concept that allows us to calculate the force on a charge when multiple charges are present?

<p>The superposition principle</p> Signup and view all the answers

The electric field due to a charge is unaffected by the presence of other charges.

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

What is the SI unit of electric field?

<p>Newton per Coulomb (N/C)</p> Signup and view all the answers

The electric field due to a charge is numerically equal to the force that the charge exerts on a unit negative charge.

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

What is the electric field due to a charge q at a point r from the charge defined as?

<p>The force that a unit positive charge would experience if placed at that point</p> Signup and view all the answers

The electric field due to a charge Q is independent of the test charge q.

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

The electric field due to a positive charge is directed radially outwards from the charge.

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

The electric field due to a negative charge is directed radially inwards from the charge.

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

The magnitude of the electric field due to a point charge is the same at all points at a given distance from the charge.

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

The electric field due to a point charge has spherical symmetry.

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

What is the electric field due to a system of charges defined as?

<p>The force experienced by a unit test charge placed at that point, without disturbing the original positions of the charges</p> Signup and view all the answers

We can use Coulomb's law and the superposition principle to determine the electric field at a point due to a system of charges.

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

The electric field is a scalar quantity.

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

Why was the concept of the electric field introduced?

<p>To understand the time delay between the effect of a moving charge and the resulting force on another distant charge.</p> Signup and view all the answers

Study Notes

Static Electricity and Electric Discharge

  • The phenomenon that causes a spark or crackle when we take off synthetic clothes is called static electricity.
  • Another common example of electric discharge is lightning.
  • The term "Static" in the context of electrostatics means stationary or at rest.
  • The Greek word from which the term "electricity" is derived is "elektron", meaning amber.
  • When two glass rods rubbed with a wool or silk cloth are brought close to each other, they repel each other.
  • When a glass rod rubbed with wool is brought close to a piece of silk cloth, they attract each other.
  • The property that differentiates the two kinds of charges is called the polarity of charge.
  • When an electrified glass rod is brought in contact with the silk cloth with which it was rubbed, the charges neutralize each other.
  • The American scientist who named charges as positive and negative was Benjamin Franklin.
  • The simple apparatus used to detect charge on a body is called an electroscope.
  • The degree of divergence of the gold leaves in an electroscope is an indicator of the amount of charge on the body.

The Nature of Charge

  • Material bodies acquire charge due to the transfer of electrons from one body to another.
  • When a body loses some of its electrons, it becomes positively charged.
  • When a body gains electrons, it becomes negatively charged.
  • New charges are not created during the process of rubbing.
  • The number of electrons transferred during rubbing is a significant fraction of the total number of electrons in the material body.

Conductors and Insulators

  • Substances that readily allow the passage of electricity through them are called conductors.
  • Substances that offer high resistance to the passage of electricity through them are called insulators.
  • Examples of conductors include metals, human and animal bodies, and earth.
  • Examples of insulators include glass, porcelain, plastic, nylon, and wood.
  • When some charge is transferred to a conductor, it spreads uniformly over the surface.
  • When some charge is put on an insulator, it stays concentrated on the surface where the charge is applied.
  • Charges on a metal object that leak through our body to the ground are discharged.
  • A metal rod with a wooden or plastic handle, when rubbed, will show signs of charging because the handle prevents the charge from leaking away.

Quantization of Charge

  • If the sizes of charged bodies are very small compared to the distances between them, we often treat them as point charges.
  • The total charge of a system containing charges of +1, +2, -3, +4, and -5, in some arbitrary unit, is -1.
  • Charges are transferred in the process of rubbing, not created or destroyed.
  • If a system consists of many charged bodies, the total charge of the system is always conserved.
  • It is impossible to create or destroy net charge carried by an isolated system.
  • All free charges are integral multiples of a basic unit of charge denoted by e.
  • The charge on an electron is conventionally taken to be -e.
  • The charge on a proton is conventionally taken to be +e.

Coulomb's Law

  • Coulomb's law is a quantitative statement about the force between two point charges.
  • Coulomb's law is valid only for charges that are much smaller than the distance separating them.
  • The instrument used by Coulomb to measure the force between two charged spheres is called a torsion balance.
  • The force between two point charges is directly proportional to the product of the magnitudes of the two charges.
  • Coulomb's law was established by conducting experiments at the macroscopic level, not the subatomic level.
  • The choice of the constant k in Coulomb's law determines the units in which force, charge, and distance are measured.
  • The value of the constant k in Coulomb's law in SI units is 9 × 10⁹ Nm²/C².
  • 1 Coulomb is equivalent to a force of 9 × 10⁹ N exerted on a unit charge 1 meter away in vacuum.
  • Coulomb's law only applies to charges in vacuum.
  • The force between two point charges does not depend on the medium in which they are placed.
  • The term "permittivity" of free space means the ability of a medium to permit electric fields to pass through it.
  • The permittivity of free space is denoted by Ɛ₀.
  • The value of Ɛ₀ in SI units is 8.854 × 10⁻¹² C²/Nm².

Electric Field

  • Force is a vector quantity, meaning it has both magnitude and direction.
  • Charges add up like scalars, like the mass of a body.
  • Mass and charge are not similar to each other in terms of magnitude and direction.
  • Coulomb's law agrees with Newton's third law.
  • To calculate the force on a charge when multiple charges are present, we can use the superposition principle: the total force on a charge is the vector sum of the forces due to each individual charge.
  • The SI unit of electric field is N/C.
  • The electric field due to a charge is numerically equal to the force that the charge exerts on a unit negative charge.
  • The electric field due to a charge q at a point r from the charge is defined as E = kq/r², where k is Coulomb's constant.
  • The electric field due to a charge Q is independent of the test charge q.
  • The electric field due to a positive charge is directed radially outwards from the charge.
  • The electric field due to a negative charge is directed radially inwards from the charge.
  • The magnitude of the electric field due to a point charge is the same at all points at a given distance from the charge.
  • The electric field due to a point charge has spherical symmetry.
  • The electric field due to a system of charges is defined as the vector sum of the electric fields due to each individual charge.
  • We can use Coulomb's law and the superposition principle to determine the electric field at a point due to a system of charges.
  • The electric field is a vector quantity.
  • The concept of the electric field was introduced to describe the influence of charges on each other, even when they are not directly interacting.

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