In an interial reference frame `K` there is only magnetic field with induction `B = b (yl -x)//(x^(2) + y^(2))`, where `b` is a constane, `i` and `j` are the unit vectors of the `x` and `y` axes. Find the elecric field strength `E'` in the frame `K'` moving relative to the frame `K` with a constatn non-relative velocity `v = vk, k` is the unit vector of the z-axis. The `z'` axis is assumed to coincule with the `z` axis. What is the shape of the field `E'` ?

Explanation

In `K,vec(B) = b (y hat(i) - x hat(j))/(x^(2) + y^(2)), b` = constant.
In `K' = vec(E') = vec(v) xx vec(B) = bv (y hat(i) - x hat(j))/(x^(2) + y^(2)) = bv (vec(r))/(r^(2))`
The electric field is radial `(vec(r) = x hat(i) + y hat(j))`