Using the Lorentz force law for my problem, I get the following matrix.

I ex ey ez I

I 1 . -1 . 0 I

I 1 . 0 . -1 I

I have evaluated the ey term as a -ve ( ey((1X-1)-(0x1)) = ey(-1-0) = -1ey)

= ex((-1x-1)-(0x0)) + ey((1X-1)-(0x1)) + ez ((1x0)-(-1x1))

= e_{x}- e_{y}+ e_{z }Another person evaluates this term as +ve. so could someone point out the obvious mistake I made, please, I can't see it.

The set problem is

An electron in a magnetic fieldB=2.0T(e_{x}-e_{z}) has velocity v=(2.5x10^{7}ms-1 (e_{x}-e_{y})

a) calculate magnetic force on electron at that instant

Now, F = -e 2(2.5x10^{7}) (e_{x}-e_{z})* (e_{x}-e_{y})

so

F = -8x10-12 (e_{x}- e_{y}+ e_{z})