# Lorentz force law equation

1. Jan 2, 2014

### divyashree

How do we say that F=BIL SINΘ using the SI units?
newton(N)= Weber/m2 * ampere*meter.

please explain as soon as possible.

2. Jan 2, 2014

### Alpharup

Use magnetic lorentz force on a charged particle equation. And you can prove

F=BqvsinΘ.(Magnitude only).

so B= F/qvsinΘ
So, the unit of B is N/C(ms^(-1))

multiply s on both numerator and denominator,

so the unit is Ns/Cm

But F = BILsinΘ (Force on current carrying wire)

Unit of RHS is therefore

=(Ns/Cm)Am
Here A is ampere But A=Cs^(-1)

Substituting, you get the unit as N which is the unit of LHS

Last edited: Jan 2, 2014
3. Jan 2, 2014

### mishima

A Weber is also energy in joules (stored in field) per ampere. So the amperes and numerator meter cancel and you are left with force (N) = energy (J) / length (m)...which is true since work is force times displacement. You could also break the Joule down into (mass * velocity squared) kg*m^2/s^2. Observe dividing a meter gives you the Newton (mass * acceleration) (kg*m/s^2).