Define Coulomb's law .

Coulomb's law states that the electrostatic force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of their separation.

Define permittivity of free space (ε 0 ).

Permittivity of free space is a measure of the resistance offered by a material in creating an electric field within it; in a vacuum, ε 0 = 8.85 × 10 -12 C 2 N -1 m -2 .

For two charges of the same type, the product Q 1 Q 2 is .......... , meaning the charges experience repulsion.

For two charges of the same type, the product Q 1 Q 2 is positive , meaning the charges experience repulsion.

What condition must be satisfied for the point charge approximation to be valid when applying Coulomb's law to charged spheres?

The size of the charged spheres must be much smaller than their separation, and the separation r must be measured between the centres of the spheres.

True or False? Coulomb's law can be used to calculate the electrostatic force between charges distributed on an irregularly shaped object.

False. Coulomb's law only applies to charged spheres that can be treated as point charges; it cannot be used for charges distributed on irregularly shaped objects.

How is a uniform, charged spherical conductor treated when calculating the electric field outside it?

It is treated as a point charge located at its centre, so the field lines around it are identical to those around a point charge.

Define electric field lines .

Electric field lines represent the direction and magnitude of an electric field; they are always directed from the positive charge to the negative charge.

Describe the field lines in a uniform electric field, and what this means for field strength.

In a uniform field, the field lines are equally spaced at all points; the electric field strength is constant everywhere, and the force on a test charge has the same magnitude and direction at all points.

Describe the field lines in a radial electric field, and what this means for field strength.

In a radial field, the field lines are equally spaced at the surface of the charge, but their separation increases with distance; this means the field strength and the force on a test charge decrease with distance.

Around a point charge, the field lines point radially .......... for a positive charge and radially inwards for a negative charge.

Around a point charge, the field lines point radially outwards for a positive charge and radially inwards for a negative charge.

How is a charged conducting sphere treated when determining its surrounding electric field?

The field around it is the same as if all the charge were concentrated at its centre , so it can be treated in the same way as a point charge .

True or False? The field lines between two charges of the same type touch the surfaces of both charges, in the same way as they do for two opposite charges.

False. For two like charges, the field lines are directed away from (or towards) each charge but do not connect the surfaces of the two charges, representing repulsion rather than attraction.

Describe the electric field beyond the edges of two parallel charged plates.

Beyond the edges of the plates, the electric field is non-uniform (in contrast to the uniform field between the plates).

Define electric field strength at a point.

Electric field strength at a point is the force per unit charge experienced by a small positive test charge placed at that point.

The definition of electric field strength specifies that a small, .......... test charge is used, which sets the convention for the direction of an electric field.

The definition of electric field strength specifies that a small, positive test charge is used, which sets the convention for the direction of an electric field.

In a field of strength E , in what direction is the force on a positive charge, and on a negative charge?

A positive charge + Q experiences a force EQ in the direction of the field ; a negative charge − Q experiences a force EQ in the opposite direction .

True or False? Electric field strength is a scalar quantity.

False. Electric field strength is a vector quantity, always directed away from a positive charge and towards a negative charge.

Define an electric field .

An electric field is a region of space in which an electric charge experiences a force .

How does the electric field strength between two parallel plates change with (a) increasing voltage and (b) increasing plate separation?

The greater the voltage between the plates, the stronger the field The greater the separation between the plates, the weaker the field

The two units for electric field strength, V m -1 and N C -1 , are .......... .

The two units for electric field strength, V m -1 and N C -1 , are equivalent .

In which direction does the electric field point between two charged parallel plates?

From the positive plate (connected to the positive terminal) to the negative plate (connected to the negative terminal).

True or False? The equation E = V / d can be used to calculate the electric field strength around a point charge.

False. E = V / d only applies to the uniform field between parallel plates; the field around a point charge is radial , so this equation cannot be used.

Describe the motion of a charged particle that is (a) stationary and (b) moving through a uniform electric field.

A stationary charged particle moves parallel to the field lines (along or against them, depending on its charge) A charged particle already moving through the field travels in a parabolic trajectory , due to the constant electric force acting on it

Between two charged parallel plates, which plate does a positive charge deflect towards, and which does a negative charge deflect towards?

A positive charge deflects towards the negative plate A negative charge deflects towards the positive plate

What happens to an uncharged particle, such as a neutron, passing between charged parallel plates?

It experiences no force , so it travels straight through the plates undeflected.

The greater the .......... of a charged particle, the smaller its deflection in a uniform electric field.

The greater the mass of a charged particle, the smaller its deflection in a uniform electric field.

How does the magnitude of a particle's charge affect its deflection in a uniform electric field (all else being equal)?

The greater the magnitude of the charge, the greater the deflection.

How does a particle's speed affect its deflection in a uniform electric field (all else being equal)?

The greater the speed of the particle, the smaller the deflection.

True or False? As a charged particle travels through a uniform electric field, the force on it changes in magnitude and direction, causing its parabolic path to curve more sharply over time.

False. The electric force on the particle is the same at all points and always in the same direction ; the parabolic path results from this constant force, not a changing one.

How does the electric field strength vary (a) inside and (b) outside a uniformly charged sphere?

Inside the sphere, the field strength is zero Outside the sphere, the field strength decreases with distance following an inverse square law

In a radial field, the electric field strength E is not constant and follows an .......... law with distance r .

In a radial field, the electric field strength E is not constant and follows an inverse square law with distance r .

For a point on the same line as two charges, how is the resultant field found if the two fields point (a) in the same direction and (b) in opposite directions?

Same direction : the resultant is the sum of the fields, E 1 + E 2 Opposite directions : the resultant is the difference between the fields, E 1 − E 2

How is the resultant electric field found at a point that forms a right-angled triangle with two charges?

The resultant field is found by vector addition of the field components from both charges, using Pythagoras' theorem .

What two factors determine the direction of the resultant electric field due to multiple charges?

The types of charge (positive or negative) The magnitude of the charges

True or False? For a negative point charge, the electric field points away from the centre of the charge.

False. For a negative charge, the electric field strength is negative and points towards the centre of the charge; it only points away from the centre for a positive charge.

What type of quantity does the gravitational force act on, and what type does the electrostatic force act on?

Gravitational force acts on particles with mass Electrostatic force acts on particles with charge

Is the gravitational force always attractive, and can the electrostatic force be repulsive?

The gravitational force is always attractive The electrostatic force can be attractive or repulsive

The gravitational potential is always .......... , whilst the electric potential can be either negative or positive.

The gravitational potential is always negative , whilst the electric potential can be either negative or positive.

Why are gravitational fields relatively weak compared to electric fields?

Gravitational fields are relatively weak because the gravitational constant G is much smaller than the Coulomb constant k .

Describe the shape of the equipotential surfaces in a radial field and in a uniform field.

Radial field (around a point mass or point charge): spherical Uniform field : equally spaced parallel lines

How do gravitational field strength and gravitational potential vary with distance in a radial field, and how do the equivalent electric quantities vary?

Field strength (gravitational and electric): inverse square law, 1/r 2 Potential (gravitational and electric): inverse law, 1/r

True or False? The field lines around a point mass are identical to those around a positive point charge.

False. The field lines around a point mass are identical to those around a negative point charge , not a positive one, since both are attractive and converge inward toward the point.

What is the work done by a gravitational or electric field equal to?

The work done is equal to the product of the mass (or charge ) and the change in potential .

A LevelPhysicsAQAFlashcardsFields & Their ConsequencesElectric Fields

Electric Fields (AQA A Level Physics): Flashcards

Exam code: 7408

1/49

0Still learning

Know0

FrontCoulomb's Law
Define Coulomb's law.
FrontCoulomb's Law
State the equation for Coulomb's law, including the meaning of each symbol.
BackCoulomb's Law
$F = \frac{Q_{1} Q_{2}}{4 π ϵ_{0} r^{2}}$
F = electrostatic force between the charges (N)
Q₁, Q₂ = magnitudes of the charges (C)
r = distance between the centres of the charges (m)
ε₀ = permittivity of free space

Was this flashcard helpful?

Cards in this collection (49)

Define Coulomb's law.
Coulomb's law states that the electrostatic force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of their separation.
State the equation for Coulomb's law, including the meaning of each symbol.
$F = \frac{Q_{1} Q_{2}}{4 π ϵ_{0} r^{2}}$
- F = electrostatic force between the charges (N)
- Q₁, Q₂ = magnitudes of the charges (C)
- r = distance between the centres of the charges (m)
- ε₀ = permittivity of free space
Define permittivity of free space (ε₀).
Permittivity of free space is a measure of the resistance offered by a material in creating an electric field within it; in a vacuum, ε₀ = 8.85 × 10^-12 C² N^-1 m^-2.
For two charges of the same type, the product Q₁Q₂ is .........., meaning the charges experience repulsion.
For two charges of the same type, the product Q₁Q₂ is positive, meaning the charges experience repulsion.
What condition must be satisfied for the point charge approximation to be valid when applying Coulomb's law to charged spheres?
The size of the charged spheres must be much smaller than their separation, and the separation r must be measured between the centres of the spheres.
True or False?
Coulomb's law can be used to calculate the electrostatic force between charges distributed on an irregularly shaped object.
False.
Coulomb's law only applies to charged spheres that can be treated as point charges; it cannot be used for charges distributed on irregularly shaped objects.
How is a uniform, charged spherical conductor treated when calculating the electric field outside it?
It is treated as a point charge located at its centre, so the field lines around it are identical to those around a point charge.
Define electric field lines.
Electric field lines represent the direction and magnitude of an electric field; they are always directed from the positive charge to the negative charge.
Describe the field lines in a uniform electric field, and what this means for field strength.
In a uniform field, the field lines are equally spaced at all points; the electric field strength is constant everywhere, and the force on a test charge has the same magnitude and direction at all points.
Describe the field lines in a radial electric field, and what this means for field strength.
In a radial field, the field lines are equally spaced at the surface of the charge, but their separation increases with distance; this means the field strength and the force on a test charge decrease with distance.
Around a point charge, the field lines point radially .......... for a positive charge and radially inwards for a negative charge.
Around a point charge, the field lines point radially outwards for a positive charge and radially inwards for a negative charge.
How is a charged conducting sphere treated when determining its surrounding electric field?
The field around it is the same as if all the charge were concentrated at its centre, so it can be treated in the same way as a point charge.
True or False?
The field lines between two charges of the same type touch the surfaces of both charges, in the same way as they do for two opposite charges.
False.
For two like charges, the field lines are directed away from (or towards) each charge but do not connect the surfaces of the two charges, representing repulsion rather than attraction.
Describe the electric field beyond the edges of two parallel charged plates.
Beyond the edges of the plates, the electric field is non-uniform (in contrast to the uniform field between the plates).
Define electric field strength at a point.
Electric field strength at a point is the force per unit charge experienced by a small positive test charge placed at that point.
State the equation for electric field strength, including the units of each term.
$E = \frac{F}{Q}$
- E = electric field strength (N C^-1)
- F = electric force on the charge (N)
- Q = magnitude of the charge (C)
The definition of electric field strength specifies that a small, .......... test charge is used, which sets the convention for the direction of an electric field.
The definition of electric field strength specifies that a small, positive test charge is used, which sets the convention for the direction of an electric field.
In a field of strength E, in what direction is the force on a positive charge, and on a negative charge?
A positive charge +Q experiences a force EQ in the direction of the field; a negative charge −Q experiences a force EQ in the opposite direction.
True or False?
Electric field strength is a scalar quantity.
False.
Electric field strength is a vector quantity, always directed away from a positive charge and towards a negative charge.
Define an electric field.
An electric field is a region of space in which an electric charge experiences a force.
State the equation for the electric field strength between two parallel plates, including the units of each term.
$E = \frac{V}{d}$
- E = electric field strength (V m^-1)
- V = potential difference between the plates (V)
- d = separation between the plates (m)
How does the electric field strength between two parallel plates change with (a) increasing voltage and (b) increasing plate separation?
- The greater the voltage between the plates, the stronger the field
- The greater the separation between the plates, the weaker the field
The two units for electric field strength, V m^-1 and N C^-1, are ...........
The two units for electric field strength, V m^-1 and N C^-1, are equivalent.
In which direction does the electric field point between two charged parallel plates?
From the positive plate (connected to the positive terminal) to the negative plate (connected to the negative terminal).
True or False?
The equation E = V/d can be used to calculate the electric field strength around a point charge.
False.
E = V/d only applies to the uniform field between parallel plates; the field around a point charge is radial, so this equation cannot be used.
State the equation for the work done W when a charge Q moves through a potential difference V.
$W = Q V$
State the equation for the work done W on a charge in terms of the electrostatic force F and the distance d moved between the plates.
$W = F d$
Describe the motion of a charged particle that is (a) stationary and (b) moving through a uniform electric field.
- A stationary charged particle moves parallel to the field lines (along or against them, depending on its charge)
- A charged particle already moving through the field travels in a parabolic trajectory, due to the constant electric force acting on it
Between two charged parallel plates, which plate does a positive charge deflect towards, and which does a negative charge deflect towards?
- A positive charge deflects towards the negative plate
- A negative charge deflects towards the positive plate
What happens to an uncharged particle, such as a neutron, passing between charged parallel plates?
It experiences no force, so it travels straight through the plates undeflected.
The greater the .......... of a charged particle, the smaller its deflection in a uniform electric field.
The greater the mass of a charged particle, the smaller its deflection in a uniform electric field.
How does the magnitude of a particle's charge affect its deflection in a uniform electric field (all else being equal)?
The greater the magnitude of the charge, the greater the deflection.
How does a particle's speed affect its deflection in a uniform electric field (all else being equal)?
The greater the speed of the particle, the smaller the deflection.
True or False?
As a charged particle travels through a uniform electric field, the force on it changes in magnitude and direction, causing its parabolic path to curve more sharply over time.
False.
The electric force on the particle is the same at all points and always in the same direction; the parabolic path results from this constant force, not a changing one.
State the equation for the electric field strength due to a point charge, including the units of each term.
$E = \frac{F}{q} = \frac{Q}{4 π ϵ_{0} r^{2}}$
- Q = the point charge producing the field (C)
- r = distance from the centre of the charge (m)
- ε₀ = permittivity of free space (F m^-1)
How does the electric field strength vary (a) inside and (b) outside a uniformly charged sphere?
- Inside the sphere, the field strength is zero
- Outside the sphere, the field strength decreases with distance following an inverse square law
In a radial field, the electric field strength E is not constant and follows an .......... law with distance r.
In a radial field, the electric field strength E is not constant and follows an inverse square law with distance r.
For a point on the same line as two charges, how is the resultant field found if the two fields point (a) in the same direction and (b) in opposite directions?
- Same direction: the resultant is the sum of the fields, E₁ + E₂
- Opposite directions: the resultant is the difference between the fields, E₁ − E₂
How is the resultant electric field found at a point that forms a right-angled triangle with two charges?
The resultant field is found by vector addition of the field components from both charges, using Pythagoras' theorem.
What two factors determine the direction of the resultant electric field due to multiple charges?
- The types of charge (positive or negative)
- The magnitude of the charges
True or False?
For a negative point charge, the electric field points away from the centre of the charge.
False.
For a negative charge, the electric field strength is negative and points towards the centre of the charge; it only points away from the centre for a positive charge.
What type of quantity does the gravitational force act on, and what type does the electrostatic force act on?
- Gravitational force acts on particles with mass
- Electrostatic force acts on particles with charge
Is the gravitational force always attractive, and can the electrostatic force be repulsive?
- The gravitational force is always attractive
- The electrostatic force can be attractive or repulsive
The gravitational potential is always .........., whilst the electric potential can be either negative or positive.
The gravitational potential is always negative, whilst the electric potential can be either negative or positive.
Why are gravitational fields relatively weak compared to electric fields?
Gravitational fields are relatively weak because the gravitational constant G is much smaller than the Coulomb constant k.
Describe the shape of the equipotential surfaces in a radial field and in a uniform field.
- Radial field (around a point mass or point charge): spherical
- Uniform field: equally spaced parallel lines
How do gravitational field strength and gravitational potential vary with distance in a radial field, and how do the equivalent electric quantities vary?
- Field strength (gravitational and electric): inverse square law, 1/r²
- Potential (gravitational and electric): inverse law, 1/r
True or False?
The field lines around a point mass are identical to those around a positive point charge.
False.
The field lines around a point mass are identical to those around a negative point charge, not a positive one, since both are attractive and converge inward toward the point.
What is the work done by a gravitational or electric field equal to?
The work done is equal to the product of the mass (or charge) and the change in potential.

Sign up to unlock flashcards

By signing up you agree to our Terms and Privacy Policy

Previous:Orbits of Planets & SatellitesNext:Electric Potential