# Problem in magnetic effects of current

1. Apr 26, 2010

### logearav

1. The problem statement, all variables and given/known data

a long straight wire carries a current of 2A. an electron travels with a speed of 4*10^4 m/s parallel to the wire at a distance of 0.1 metre from it. what force does the magnetic field exert on the moving electron

2. Relevant equations
what formula should i use? is it f= BqV SIN$$\theta$$ or f= BIl sin$$\theta$$
or f=4*3.14*10^-7* I1*I2* L)/(2*3.14*a)
he attempt at a solution[/b]
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Apr 27, 2010

### Redbelly98

Staff Emeritus
A reasonable question. Here's a hint: does the question ask for the force on a single charge, or the force on a current-carrying wire?

3. Apr 28, 2010

### logearav

"a long straight wire carries a current of 2A. an electron travels with a speed of 4*10^4 m/s parallel to the wire at a distance of 0.1 metre from it. what force does the magnetic field exert on the moving electron"
the problem is like this. nothing mentioned extra.

4. Apr 28, 2010

### Redbelly98

Staff Emeritus
You didn't really answer my question, which was meant to be a hint to help you decide which equation to use.

5. Apr 28, 2010

### Redbelly98

Staff Emeritus
To make my point clearer:
That is the force on a charge q moving with speed V.

This is the force on a wire of length l and current I.

This one is the force between two wires of length L.

So, to figure out which equation applies here, you need to figure out if you need the force on a single charge, the force acting on a single wire, or the force acting between a pair of wires.