# Cartesian coordinates vectors

## The Attempt at a Solution

the answer given is the same but without the negative sign, I don't understand because the crossproduct of unit vectors

when using a Cartesian coordinates of the directions given by the right-hand rule? Is the positive z direction pointing out of the page if X and Y are as follows

apologies if this is in the wrong section, thanks for any help in advance

Related Introductory Physics Homework Help News on Phys.org
BvU
Homework Helper
2019 Award
Yes. $\hat {k} = \hat {\bf \imath } \times\hat {\bf \jmath}$ , so z points towards you, out of the screen.

Corkscrew rule I call it. Turn $\hat{\bf \imath }$ over the smallest angle towards $\hat {k}$. Corkscrew will go in the minus y direction : $$\hat \imath \times\hat k = -\hat \jmath$$

TSny
Homework Helper
Gold Member
The problem doesn't specify which of the two wires the charge -q is a distance b from. Does the answer change if you pick the other wire to be a distance b from -q?

BvU
Thank you both your answers, TSny I thought the same, closer to the top wire the combined magnetic field would be in the opposite direction . Maybe the question is just not very good