Problem in magnetic effects of current

[logearav]

Homework Statement

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

Homework 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]

 

[Redbelly98]

Homework 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]

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?

 

[logearav]

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?

"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.

 

[Redbelly98]

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

 

[Redbelly98]

To make my point clearer:

what formula should i use? is it f= BqV SIN$$\theta$$

That is the force on a charge q moving with speed V.

... or f= BIl sin$$\theta$$

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

... or f=4*3.14*10^-7* I1*I2* L)/(2*3.14*a)

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.