1. Electric Fields

2. Electric Fields
Electric field strength is force per unit POSITIVE charge
𝑬= 𝑭 𝑸
Unit NC-1
Electric field lines always run away from positive and towards negative.

3. Electric Fields
This is because if you place a positive charge in an electric field it will be repelled away from a positive charge whereas it will be attracted towards a negative charge.
The closer together the field lines the stronger the field
In radial fields the field strength decreases according to the inverse square law.

4. Radial Electric Fields

5. Uniform Electric Fields
The electric field between two charged plates is a uniform electric field
The electrical field strength is directly proportional to the p.d across the plates and inversely proportional to the distance between them.
Hence 𝑬= 𝑽 𝒅
Unit Vm-1
Hence 1NC-1=1Vm-1

6. Uniform Electric Field

7. Coulombs law
When a charged object is placed inside an electric field it experiences a force
The force is proportional to the product of the two charges (the one creating the field and the one placed inside it) and inversely proportional to the distance between them.
Hence the two charged objects will experience the same force.

8. Coulombs Law 𝑭∝ 𝒌𝑸𝒒 𝒓 𝟐 𝒌= 𝟏 𝟒𝝅 𝜺 𝟎 𝑭= 𝑸𝒒 𝟒𝝅 𝜺 𝟎 𝒓 𝟐
𝑭∝ 𝒌𝑸𝒒 𝒓 𝟐 𝒌= 𝟏 𝟒𝝅 𝜺 𝟎
𝑭= 𝑸𝒒 𝟒𝝅 𝜺 𝟎 𝒓 𝟐
𝑬= 𝑸 𝟒𝝅 𝜺 𝟎 𝒓 𝟐 (as E=F/Q)
4π refers to the radial field and ε0 is the permittivity of free space 8.85*10-12Fm

9. Forces on particles moving through uniform electric fields
A charged particle moving through a uniform electric field will be deflected up or down depending on its charge as it experiences a force
It’s path will be a parabola as it will be accelerating vertically due to the force acting on it, but it’s horizontal velocity will remain constant
The force the particle experiences is given by F=EQ
Since E=V/d,
𝑭= 𝑸𝑽 𝒅

10. Comparing gravitational and electric fields
Similarities
They both obey the inverse square law
They both have either radial or parallel field lines
They are both force per unit…

11. Comparing gravitational and electric fields
Differences
Gravitational fields are created by mass, electrical fields are created by charge
Gravitational fields are only attractive, electrical fields can be attractive and repulsive.
You can be shielded from an electric field but not from a gravitational field.