Electric fields (Edexcel GCSE Physics): Revision Notes
Electric fields
An electric field is created around any electrically charged object. It is the region around a charged object where another charged object would experience a force.
- If a second charged object is placed in this field, it either feels an attractive or repulsive force, depending on the charges.
- The closer you are to the charged object, the stronger the electric field.
- The strength of the electric field decreases with distance from the charged object.
Sparks and Electric Fields
How Sparks are Caused:
When an object becomes statically charged, it creates its own electric field. If there is a high enough potential difference (voltage) between the charged object and the Earth (or another earthed object), it can cause a spark.
Steps in Spark Formation:
- High potential difference creates a strong electric field between the charged object and the Earth.
- This strong field can cause the air particles to become ionised, meaning electrons are removed from the air molecules.
- Once the air is ionised, it becomes more conductive, allowing current to flow through the air.
- This flow of current is seen as a spark.
Electrostatic Forces
Electrostatic forces are forces that charged objects experience in an electric field.
If a charged object is placed in the field of another charged object, the fields interact, causing the objects to feel a force.
- Like charges (e.g., two positive charges) repel each other.
- opposite charges (e.g., one positive and one negative) attract each other.
Electric Field Lines
Electric field lines help us visualise the direction and strength of an electric field.
- Field lines point from positive to negative charges.
- The closer together the lines, the stronger the field.
- When two charged objects interact, the electric field lines behave differently depending on the charges:
- Same Charges (Repulsion):
- Field lines will push against each other.
- The objects will repel each other because their electric fields do not overlap.
- Opposite Charges (Attraction):
- Field lines will join up between the two objects.
- The objects will attract each other because their electric fields pull them together.
Uniform Electric Fields
A uniform electric field is created when the electric field strength is the same at all points in a region.
This happens between two oppositely charged parallel plates.
- The field lines are parallel and evenly spaced, showing that the field strength and direction are consistent anywhere between the plates (except at the edges).