- #1

majormaaz

- 62

- 1

## Homework Statement

A point charge q = -2.9 μC moves along the z-axis with a velocity v

^{→}= (+7.3 x 10

^{5}m/s) k . At the moment it passes the origin, what are the strength and direction of the magnetic field at the following positions? Express each field vector in Cartesian form.

(a) At position r

_{1}= (2.0 cm, 0 cm, 0 cm)

(b) At position r

_{2}= (0 cm, 4.0 cm, 0 cm).

(c) At position r

_{3}= (0 cm, 0 cm 1.5 cm).

(d) At position r

_{4}= (3.5 cm, 1.5 cm, 0 cm).

(e) At position r

_{5}= (3.0 cm, 0 cm, 1.0 cm)

## Homework Equations

B

_{point charge}= [μ

_{0}/4pi] * [qv x sin Θ / r

^{2}]

## The Attempt at a Solution

I saw that this problem has a negative charge, so I'd have to use the RHR and reverse direction to account for the charge being negative. I also got the fact that the magnetic field at a point along the same axis as the charge's velocity is 0 Teslas.

I ended up with

(a) 0 i + _ j + 0 k

(b) _ i + 0 j + 0 k

(c) 0 i + 0 j + 0 k

(d) _ i + _ j + 0 k

(e) 0 i + _ j + 0 k

However, everytime I used the point charge formula I have, I end up with an incorrect answer. For example, in part (a), with a r = 2 cm = 0.02 m, I plugged that into [μ

_{0}/4pi] * [|q|v x sin Θ / r

^{2}], and then reversing the sign to account for a negative charge, but it didn't work.

i.e. I calculated that for part (a), a value of 2 cm for r would have a magnetic field of -5.29e-4 T in the j direction, but that's apparently not right.