**Similar to how the Electric Field is defined using the Electrostatic Force, specifically the influence of an electric force, we can also define a magnetic field.
Definition
The strength of the field is given by the Biot-Savart Law:
It is defined by the unit Tesla, . Sometimes, the unit gauss is used as well,
Visualising
Unlike electric fields, magnetic fields require a moving charge, and due to the cross product, operate in a more ‘3D’ space, making them harder to visualise. Here’s an attempt:
The 2D view makes things, far far easier to understand.
When drawing magnetic fields, field lines can be used to visualise the magnetic field around a point. As it is a vector field, we can observe the direction from the field lines to identify the force. However, there are some important rules:
- Field lines exist always exist as loops. #ask why?
- They cannot intersect or touch
- The density of the field lines is used to identify the field strength, not the length of the field lines. I.e. areas where there is a lot of field lines bunched up indicate a stronger magnetic field. Note the denser magnetic field closer to the charge.
- Areas where the electric field is 0 is marked with a dot or a gap
Superposition
Being a vector field, magnetic fields can also be superposed onto each other, resulting in a different net magnetic field: