Working in CGS units, we first need to find the form of the electric and magnetic fields. The fields can be written (for a fuller derivation see Liénard–Wiechert potential) E ( r , t ) = q ( n − − β β γ γ 2 ( 1 − − β β ⋅ ⋅ n ) 3 R 2 ) ret + q c ( n × × [ ( n − − β β ) × × β β ˙ ˙ ] ( 1 − − β β ⋅ ⋅ n ) 3 R ) ret and B = n × × E , where β β is the charge's velocity divided by c , β β ˙ ˙ is the charge's acceleration divided by c, n is a unit vector in the r − − r 0 direction, R is the magnitude of r − − r 0 , r 0 is the charge's location, and γ γ = ( 1 − − β β 2 ) − − 1 / 2 . The terms on the right are evaluated at the retarded time t r = t − − R / c .