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## Homework Statement

An electron in a magnetic field

**B**=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

b) what is the magnitude of this force

## Homework Equations

I am using the Lorentz force law.

F = q(vXB)

& evaluating the directions by vector

**My argument is that the e**

_{y}term is negative, but another person evaluates this as positive. Please confirm whether I'm right or wrong.This affects the outcome of magnitude of force, too.

## The Attempt at a Solution

F = -e 2(2.5x10

^{7}) (

**e**

_{x}-

**e**

_{z})* (

**e**

_{x}-

**e**

_{y})

I ex ey ez I

I 1 . -1 . 0 I

I 1 . 0 . -1 I

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

= e

_{x}- e

_{y}+ e

_{z})

so

F = -8x10-12 (e

_{x}- e

_{y}+ e

_{z})