What do electric field lines represent, and how is the strength of the field indicated by them?

Electric field lines show the direction of force on a positive test charge. The density (closeness) of the lines indicates the field strength — closer lines mean a stronger field.

In which direction do electric field lines point?

They point in the direction of the force that would act on a positive test charge placed in the field.

State the definition of electric field strength.

Electric field strength is the force per unit positive charge.

Write the equation that defines electric field strength in terms of force and charge, and state what each symbol represents.

E = F/Q, where E is electric field strength, F is the force on the charge, and Q is the magnitude of the charge.

Calculate the electric field strength when force on charge = 1.18 N, charge = 0.000653 C.

Electric field strength = 1.18 ÷ 0.000653 = 1810 N C⁻¹.

Give the SI unit of electric field strength.

Newtons per coulomb (N C⁻¹).

AQA A-Level Physics 7408

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Fields and Their Consequences

Electric field strength

4 things to know
Papers 2 and 3

Overview

Field strength in uniform and radial fields, E = V/d, and the path of a charge in a uniform field.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

How is electric field strength defined, and what do field lines represent?

Numbers

What units does electric field strength take, and how is E = V/d derived?

Numbers

How does E = V/d follow from E = F/Q, and what path does a charge take in a uniform field?

Numbers

What happens to E when the distance from a point charge doubles, and how are field patterns investigated?

Questions from this subtopic

Each one with the model answer underneath.

1
What do electric field lines represent, and how is the strength of the field indicated by them?
Model answer
Electric field lines show the direction of force on a positive test charge. The density (closeness) of the lines indicates the field strength — closer lines mean a stronger field.
2
In which direction do electric field lines point?
Model answer
They point in the direction of the force that would act on a positive test charge placed in the field.
3
State the definition of electric field strength.
Model answer
Electric field strength is the force per unit positive charge.
4
Write the equation that defines electric field strength in terms of force and charge, and state what each symbol represents.
Model answer
E = F/Q, where E is electric field strength, F is the force on the charge, and Q is the magnitude of the charge.
5
Calculate the electric field strength when force on charge = 1.18 N, charge = 0.000653 C.
Model answer
Electric field strength = 1.18 ÷ 0.000653 = 1810 N C⁻¹.
6
Give the SI unit of electric field strength.
Model answer
Newtons per coulomb (N C⁻¹).

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