Define electric field .

A region of space in which a charged particle experiences a force .

What type of field is an electric field?

An electric field is a type of force field .

A charged particle in an electric field experiences a force whether it is ..........

A charged particle in an electric field experiences a force whether it is stationary or moving

True or False? A charged particle only experiences a force in an electric field when it is moving.

False. A charged particle experiences an electric force whether it is stationary or moving . It is in a magnetic field that a charge only experiences a force when it is moving .

Do like charges attract or repel?

Like charges (both positive or both negative) repel . Opposite charges attract .

How does the electrostatic force between two charges change as their separation increases?

The force decreases as the distance between the charges increases.

Define electric field strength .

The force per unit charge acting on a positive test charge at that point.

Electric field strength is the force per unit charge acting on a .......... test charge

Electric field strength is the force per unit charge acting on a positive test charge

In which directions does the electric field strength vector point?

Away from a positive charge and towards a negative charge.

True or False? Electric field strength is a scalar quantity

False. Electric field strength is a vector quantity — it has both magnitude and direction.

State Coulomb's law .

The electrostatic force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation .

Coulomb's law states the electrostatic force is inversely proportional to the .......... of the separation between the charges

Coulomb's law states the electrostatic force is inversely proportional to the square of the separation between the charges

What do the signs of the electrostatic force tell you about two charges?

A negative force is an attractive force (opposite charges). A positive force is a repulsive force (like charges).

Define the permittivity of free space ( ε 0 ).

A physical constant representing the capability of a vacuum to permit electric fields.

True or False? Doubling the distance between two point charges halves the electrostatic force between them.

False. The electrostatic force follows an inverse square law , so doubling the distance reduces the force to a quarter of its original value.

The electric field strength around a point charge obeys an .......... law with distance

The electric field strength around a point charge obeys an inverse square law with distance

By what factor does the field strength of a point charge change when the distance is doubled?

It decreases by a factor of four , because E is proportional to 1/ r 2 .

How does the point-charge field strength equation differ from Coulomb's law in the number of charges it contains?

The field strength equation contains only one charge Q (the charge producing the field), whereas Coulomb's law contains two charges.

True or False? Like a gravitational field, the electric field of a point charge always points towards the charge.

False. Electric field lines point away from a positive charge and towards a negative charge. A gravitational field always points towards the mass.

What does the area under a graph of field strength E against distance r represent?

The change in electric potential , Δ V .

How can a charged sphere be treated when calculating its electric field?

As a point charge located at its centre .

Define electric potential .

The amount of work done per unit charge at that point in the field.

State the relationship between electric field strength and electric potential .

The electric field strength is proportional to the gradient of the electric potential.

The potential gradient in an electric field is the rate of change of electric potential with respect to .......... in the direction of the field

The potential gradient in an electric field is the rate of change of electric potential with respect to displacement in the direction of the field

How does the electric potential vary with distance around (a) a positive charge and (b) a negative charge?

around a positive charge, the potential decreases with distance around a negative charge, the potential increases with distance

True or False? A stronger electric field means the potential changes more slowly with distance.

False. A stronger electric field means the electric potential changes more rapidly with distance. A larger potential gradient corresponds to a larger field strength.

What does the gradient of a potential–distance graph give at a point?

The electric field strength E at that point.

A positive test charge has electric potential energy due to its position in a field. What two quantities does this energy depend on?

the magnitude of the charge the value of the electric potential at that point

For electric field strength, the units V m -1 are equivalent to the units ..........

For electric field strength, the units V m -1 are equivalent to the units N C -1

How does the field strength between two parallel plates depend on the voltage and the separation of the plates?

the greater the potential difference , the stronger the field the greater the separation , the weaker the field

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

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

Define the electric potential at a point.

The work done per unit charge in bringing a positive test charge from infinity to that point.

Is electric potential a scalar or a vector quantity?

A scalar quantity — it has no direction (though it can be positive or negative depending on the sign of the charge).

Electric potential is .......... around an isolated positive charge and .......... around an isolated negative charge

Electric potential is positive around an isolated positive charge and negative around an isolated negative charge

As a positive test charge moves closer to (a) a positive charge and (b) a negative charge, what happens to its electric potential?

closer to a positive charge → potential increases (more positive) closer to a negative charge → potential decreases (more negative)

In which direction are electric field lines always directed?

From the positive charge to the negative charge — the direction of the force on a positive test charge.

How does the spacing of the field lines differ between a uniform field and a radial field?

uniform field: lines are equally spaced at all points, so field strength is constant radial field: lines get further apart with distance, so field strength decreases

How are the field lines directed around (a) a positive point charge and (b) a negative point charge?

positive charge: field lines point radially outwards negative charge: field lines point radially inwards

A charged conducting sphere produces the same field as if all its charge were concentrated at its .......... , so it can be treated as a ..........

A charged conducting sphere produces the same field as if all its charge were concentrated at its centre , so it can be treated as a point charge

Define equipotential lines .

Lines (or surfaces in 3D) that join together points having the same electric potential .

What is the angle between equipotential lines and electric field lines?

They are always perpendicular (90°) to each other, in both radial and uniform fields.

True or False? Equipotential lines have arrows to show their direction.

False. Equipotential lines have no arrows — they have no particular direction and are not vectors. Only field lines carry arrows.

What shape are the equipotential lines for (a) a radial field and (b) a uniform field?

radial field: concentric circles that become further apart with distance uniform field: equally spaced, parallel straight lines

A LevelPhysicsEdexcelFlashcards7. Electric & Magnetic FieldsElectric Fields

Electric Fields (Edexcel A Level Physics): Flashcards

Exam code: 9PH0

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FrontDefining an Electric Field
Define electric field.

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Cards in this collection (57)

Define electric field.
A region of space in which a charged particle experiences a force.
What type of field is an electric field?
An electric field is a type of force field.
A charged particle in an electric field experiences a force whether it is ..........
A charged particle in an electric field experiences a force whether it is stationary or moving
True or False?
A charged particle only experiences a force in an electric field when it is moving.
False.
A charged particle experiences an electric force whether it is stationary or moving. It is in a magnetic field that a charge only experiences a force when it is moving.
Do like charges attract or repel?
Like charges (both positive or both negative) repel. Opposite charges attract.
How does the electrostatic force between two charges change as their separation increases?
The force decreases as the distance between the charges increases.
Define electric field strength.
The force per unit charge acting on a positive test charge at that point.
State the equation for electric field strength.
$E = \frac{F}{Q}$
where E = electric field strength, F = force and Q = charge.
Electric field strength is the force per unit charge acting on a .......... test charge
Electric field strength is the force per unit charge acting on a positive test charge
What are the SI units of electric field strength?
N C^-1 (newtons per coulomb).
In which directions does the electric field strength vector point?
Away from a positive charge and towards a negative charge.
True or False?
Electric field strength is a scalar quantity
False.
Electric field strength is a vector quantity — it has both magnitude and direction.
A charged particle experiences a force of 0.3 N in an electric field of strength 3.5 × 10⁴ N C^-1.
Calculate the charge on the particle.
$Q = \frac{F}{E} = \frac{0.3}{3.5 \times 10^{4}}$
$Q = 8.6 \times 10^{- 6} C$
State Coulomb's law.
The electrostatic force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation.
State the equation for Coulomb's law.
$F = \frac{Q_{1} Q_{2}}{4 π ε_{0} r^{2}}$
where Q₁ and Q₂ are the charges, r is their separation and ε₀ is the permittivity of free space.
Coulomb's law states the electrostatic force is inversely proportional to the .......... of the separation between the charges
Coulomb's law states the electrostatic force is inversely proportional to the square of the separation between the charges
What happens to the electrostatic force between two charges when their separation is doubled?
The force reduces to ${(\frac{1}{2})}^{2} = \frac{1}{4}$ of its original value (inverse square law).
What do the signs of the electrostatic force tell you about two charges?
A negative force is an attractive force (opposite charges). A positive force is a repulsive force (like charges).
Define the permittivity of free space (ε₀).
A physical constant representing the capability of a vacuum to permit electric fields.
True or False?
Doubling the distance between two point charges halves the electrostatic force between them.
False.
The electrostatic force follows an inverse square law, so doubling the distance reduces the force to a quarter of its original value.
What type of electric field does a point charge produce?
A radial field.
State the equation for the electric field strength at distance r from a point charge Q.
$E = \frac{Q}{4 π ε_{0} r^{2}}$
where Q is the point charge, r is the distance from its centre and ε₀ is the permittivity of free space.
The electric field strength around a point charge obeys an .......... law with distance
The electric field strength around a point charge obeys an inverse square law with distance
By what factor does the field strength of a point charge change when the distance is doubled?
It decreases by a factor of four, because E is proportional to 1/r².
How does the point-charge field strength equation differ from Coulomb's law in the number of charges it contains?
The field strength equation contains only one charge Q (the charge producing the field), whereas Coulomb's law contains two charges.
True or False?
Like a gravitational field, the electric field of a point charge always points towards the charge.
False.
Electric field lines point away from a positive charge and towards a negative charge. A gravitational field always points towards the mass.
What does the area under a graph of field strength E against distance r represent?
The change in electric potential, ΔV.
How can a charged sphere be treated when calculating its electric field?
As a point charge located at its centre.
Define electric potential.
The amount of work done per unit charge at that point in the field.
State the relationship between electric field strength and electric potential.
The electric field strength is proportional to the gradient of the electric potential.
The potential gradient in an electric field is the rate of change of electric potential with respect to .......... in the direction of the field
The potential gradient in an electric field is the rate of change of electric potential with respect to displacement in the direction of the field
How does the electric potential vary with distance around (a) a positive charge and (b) a negative charge?
- around a positive charge, the potential decreases with distance
- around a negative charge, the potential increases with distance
True or False?
A stronger electric field means the potential changes more slowly with distance.
False.
A stronger electric field means the electric potential changes more rapidly with distance. A larger potential gradient corresponds to a larger field strength.
What does the gradient of a potential–distance graph give at a point?
The electric field strength E at that point.
A positive test charge has electric potential energy due to its position in a field. What two quantities does this energy depend on?
- the magnitude of the charge
- the value of the electric potential at that point
State the equation for electric field strength between two charged parallel plates.
$E = \frac{V}{d}$
- E = electric field strength (V m^-1)
- V = potential difference between the plates (V)
- d = separation between the plates (m)
For electric field strength, the units V m^-1 are equivalent to the units ..........
For electric field strength, the units V m^-1 are equivalent to the units N C^-1
How does the field strength between two parallel plates depend on the voltage and the separation of the plates?
- the greater the potential difference, the stronger the field
- the greater the separation, the weaker the field
True or False?
The equation $E = \frac{V}{d}$ can be used to find the electric field strength around a point charge.
False.
$E = \frac{V}{d}$ only applies to the uniform field between parallel plates. A point charge produces a radial field, so you would use $E = \frac{F}{Q}$ instead.
In which direction does the electric field point between two parallel plates?
From the plate connected to the positive terminal to the plate connected to the negative terminal.
If one of two parallel plates is earthed, what is its voltage?
0 V
How do you calculate the electric force on a stationary charged particle between two parallel plates?
Find the field strength using $E = \frac{V}{d}$ , then apply:
$F = Q E$
where Q is the charge on the particle.
Define the electric potential at a point.
The work done per unit charge in bringing a positive test charge from infinity to that point.
Is electric potential a scalar or a vector quantity?
A scalar quantity — it has no direction (though it can be positive or negative depending on the sign of the charge).
State the equation for the electric potential due to a point charge.
$V = \frac{Q}{4 π ε_{0} r}$
- V = electric potential (V)
- Q = point charge producing the potential (C)
- ε₀ = permittivity of free space (F m^-1)
- r = distance from the centre of the charge (m)
Electric potential is .......... around an isolated positive charge and .......... around an isolated negative charge
Electric potential is positive around an isolated positive charge and negative around an isolated negative charge
True or False?
Both electric potential and electric field strength vary as 1/r with distance from a point charge.
False.
Electric potential varies as $V \propto \frac{1}{r}$ , but electric field strength varies as $E \propto \frac{1}{r^{2}}$ .
What is the value of the electric potential at infinity?
Zero
As a positive test charge moves closer to (a) a positive charge and (b) a negative charge, what happens to its electric potential?
- closer to a positive charge → potential increases (more positive)
- closer to a negative charge → potential decreases (more negative)
In which direction are electric field lines always directed?
From the positive charge to the negative charge — the direction of the force on a positive test charge.
How does the spacing of the field lines differ between a uniform field and a radial field?
- uniform field: lines are equally spaced at all points, so field strength is constant
- radial field: lines get further apart with distance, so field strength decreases
How are the field lines directed around (a) a positive point charge and (b) a negative point charge?
- positive charge: field lines point radially outwards
- negative charge: field lines point radially inwards
A charged conducting sphere produces the same field as if all its charge were concentrated at its .........., so it can be treated as a ..........
A charged conducting sphere produces the same field as if all its charge were concentrated at its centre, so it can be treated as a point charge
Define equipotential lines.
Lines (or surfaces in 3D) that join together points having the same electric potential.
What is the angle between equipotential lines and electric field lines?
They are always perpendicular (90°) to each other, in both radial and uniform fields.
True or False?
Equipotential lines have arrows to show their direction.
False.
Equipotential lines have no arrows — they have no particular direction and are not vectors. Only field lines carry arrows.
What shape are the equipotential lines for (a) a radial field and (b) a uniform field?
- radial field: concentric circles that become further apart with distance
- uniform field: equally spaced, parallel straight lines

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