## Section 1: Magnetic Fields

Introduction:
A moving charge or a chain of moving charges create a magnetic field around their path (velocity vector). Magnetic field is a vector so it has a magnitude and a direction. In introductory physics courses, we use some mathematical equations to find the magnitude of a magnetic field and right-hand rule for positive and electric current and left-hand rule for negative charges to find the direction of the magnetic field.

$\left&space;|&space;\vec{B}&space;\right&space;|&space;=&space;{{\mu_0}&space;\over&space;{4&space;\pi}}&space;{|q|}&space;{{|\vec{v}|}\over{d^2}}&space;\sin{\theta_{\vec{v},\vec{d}}}$
where $\left&space;|&space;\vec{B}&space;\right&space;|$ is the magnitude of the magnetic field, $\mu_0$ is the permeability of the medium in henries per meter (H/m).

Following picture:

• (Left) Right-hand rule for find the connection between direction of the motion (velocity) of a moving positive charge and the magnetic field it is generating.
• (Right) Right-hand rule for finding the connection between direction of an electric current in a wire and the magnetic field it is generating.

Summary