### Magnetic force and torque

**т** = **m** × **B**

**F** = ∇ (**m** · **B**)

**т**: magnetic torque applied on an object (Nm)

**m**: magnetic moment vector (Am^{2})

**B**: magnetic flux density (T)

**F**: magnetic force applied on an object (N)

### Newton’s second law of motion

**F** = m**a**

**F**: net external force applied on an object (N)

m: object mass (kg)

**a**: acceleration of the object (m/s^{2})

### Mass-energy equivalence

E = mc^{2}

E: equivalence energy of an object (J)

m: object mass (kg)

c: speed of light (m/s)

**Ampère’s circuital law**

∇ × **B** = *μ*_{0} **J**

∇ ×: the curl operator

**B**: magnetic flux density (T)

*μ*_{0}: vacuum permeability (H/m)

**J**: the total current density (A·m^{−2})