Podcast
Questions and Answers
The direction of the electric field $\vec{E}$ is the direction of the force on a:
The direction of the electric field $\vec{E}$ is the direction of the force on a:
- Any stationary charge
- Negative test charge
- Positive test charge (correct)
- Any moving charge
If the electric force and the electric field are known at some point, one can calculate the charge of the particle at that point.
If the electric force and the electric field are known at some point, one can calculate the charge of the particle at that point.
True (A)
What happens to the electric field at a point P if a positive source charge q is replaced with a negative source charge -q of equal magnitude?
What happens to the electric field at a point P if a positive source charge q is replaced with a negative source charge -q of equal magnitude?
- The electric field remains unchanged
- The magnitude of the electric field remains the same, but the direction reverses (correct)
- The magnitude of the electric field doubles and the direction remains the same
- The electric field becomes zero
The electric field due to a collection of charges can be calculated by arithmetically summing the electric fields due to individual charges.
The electric field due to a collection of charges can be calculated by arithmetically summing the electric fields due to individual charges.
Define an electric dipole.
Define an electric dipole.
When an electric dipole is placed in an external electric field, neutral atoms and molecules behave as ______.
When an electric dipole is placed in an external electric field, neutral atoms and molecules behave as ______.
Which expression best describes the superposition principle for electric fields?
Which expression best describes the superposition principle for electric fields?
Electric field lines can cross each other.
Electric field lines can cross each other.
Match the following charge distribution with the SI unit:
Match the following charge distribution with the SI unit:
The strength of an electric field is indicated by the closeness of the field ______.
The strength of an electric field is indicated by the closeness of the field ______.
If the charge on an object is doubled, what happens to the electric field it creates at a certain distance?
If the charge on an object is doubled, what happens to the electric field it creates at a certain distance?
Electrical conductors are materials in which all electrons are bound to atoms.
Electrical conductors are materials in which all electrons are bound to atoms.
Explain the concept of charging by induction.
Explain the concept of charging by induction.
Materials such as copper and aluminum are good electrical ______.
Materials such as copper and aluminum are good electrical ______.
Why does a charged comb attract small bits of dry paper?
Why does a charged comb attract small bits of dry paper?
The Coulomb force, like the gravitational force, is only attractive.
The Coulomb force, like the gravitational force, is only attractive.
What is the Coulomb constant?
What is the Coulomb constant?
The SI unit of charge is the ______.
The SI unit of charge is the ______.
According to Coulomb's Law, if the distance between 2 charges is doubled, the electric force between them:
According to Coulomb's Law, if the distance between 2 charges is doubled, the electric force between them:
Materials can have any arbitrary amount of electric charge.
Materials can have any arbitrary amount of electric charge.
What is the net charge of an electric dipole?
What is the net charge of an electric dipole?
The electric force between two particles is independent of the medium separating them.
The electric force between two particles is independent of the medium separating them.
What is the value of elementary charge (e)?
What is the value of elementary charge (e)?
In the absence of other charges the electric field lines for point charges extend out to ______.
In the absence of other charges the electric field lines for point charges extend out to ______.
The superposition principle states that the total electric field at a point due to multiple charges is:
The superposition principle states that the total electric field at a point due to multiple charges is:
Electric field lines must end on a charge
Electric field lines must end on a charge
What experimental apparatus did Charles Coulomb use to measure the magnitude of electric forces between charged objects?
What experimental apparatus did Charles Coulomb use to measure the magnitude of electric forces between charged objects?
The electric force is also known as the ______ force.
The electric force is also known as the ______ force.
If two neutral objects are rubbed together, what happens to their charge?
If two neutral objects are rubbed together, what happens to their charge?
A semiconductor's electrical properties cannot be modified.
A semiconductor's electrical properties cannot be modified.
Flashcards
Electric Field (E)
Electric Field (E)
The force per unit charge experienced by a positive test charge in an electric field.
Electric Force (F)
Electric Force (F)
The electric force exerted on a charge in an electric field.
Source Charge
Source Charge
Creates an electric field around itself.
Test Charge
Test Charge
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Superposition Principle (Electric Fields)
Superposition Principle (Electric Fields)
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Electric Dipole
Electric Dipole
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Coulomb's Law
Coulomb's Law
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Quantization of Electric Charge
Quantization of Electric Charge
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Electrical Conductor vs Insulator
Electrical Conductor vs Insulator
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Charging by Induction
Charging by Induction
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Volume Charge Density (ρ)
Volume Charge Density (ρ)
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Surface Charge Density (σ)
Surface Charge Density (σ)
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Linear Charge Density (λ)
Linear Charge Density (λ)
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Electric Field Lines
Electric Field Lines
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Electric Forces
Electric Forces
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Elementary Charge
Elementary Charge
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Study Notes
- The direction of an electric field (E) is the direction of the force on a positive test charge.
- E is measured in newtons per coulomb (N/C).
- E is produced by a source charge or charge distribution, not the test charge itself.
- The presence of a test charge is not necessary for E to exist; it is a property of the source.
- A test charge detects E; it exists at a point if the test charge experiences an electric force there.
- An arbitrary charge q in E experiences an electric force: F = qE.
- If q is positive, F is in the same direction as E.
- If q is negative, F and E are in opposite directions.
- To determine the direction of E, consider a point charge q (source charge).
- A test charge q₀ at point P, a distance r from q, is used.
- According to Coulomb's law, the force exerted by q on q₀ is F = k(q*q₀/r²) * unit vector.
- The unit vector is directed from q toward q₀.
- E at point P due to q is E = k(q/r²) * unit vector.
Analysis Model: Particle in a Field (Electric)
- Calculating E at a point P due to multiple point charges involves vector addition.
- The total electric field E is the vector sum of the electric fields of all charges: E = ΣEᵢ = Σk(qi/ri²) * unit vector.
- E represents the total electric field, qi is the magnitude of the ith charge, ri the distance from the charge i to point P and unit vector is unit vector that points from qi to P.
- An electric dipole consists of a positive charge q and a negative charge -q, separated by a distance 2a.
- Neutral atoms and molecules behave as dipoles when placed in an external electric field.
- Some molecules, like HCl, are permanent dipoles.
- Electric field due to a continuous charge distribution is found by dividing the distribution into small elements with charge Δq.
- The electric field due to one element is ΔE = k (Δq/r²) r(hat), the electric field at that point P.
- The total electric field is approximated by the vector sum E ≈ Σ k (Δqi/ri²) r(hat).
- As the elements get smaller the summation turns into an integral: E = ∫k (dq/r²) d(r(hat))
- Where the integration is over the entire charge distribution.
- Volume charge density (ρ) is charge per unit volume: ρ = Q/V (C/m³).
- Surface charge density (σ) is charge per unit area: σ = Q/A (C/m²).
- Linear charge density (λ) is charge per unit length: λ = Q/l (C/m).
- For non-uniform charge distribution: dq = ρ dV, dq = σ dA, dq = λ dl.
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