# Lorentz Force

1. Sep 14, 2010

### tsang

Can anybody help me that how to work out the direction of Lorentz Force? Should I work out from the formula? Thanks.

2. Sep 14, 2010

### Bob S

See thumbnail photo of an electron beam (~ 300 volts) being bent into a circle (~ 1 cm diameter arc) by a magnetic field (Helmholz coil). This is an undergraduate physics lab experiment for measuring the electron charge to mass ratio.

Bob S

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Last edited: Sep 14, 2010
3. Sep 15, 2010

### Born2bwire

The equation gives the directions.

$$\mathbf{F} = q \left( \mathbf{E} + \mathbf{v}\times\mathbf{B} \right)$$

For a positive test charge there is an electric force in the direction of the applied electric field. There is also a force in the direction of the curl of the charge's velocity and the applied magnetic field. Together these define the Lorentz force.

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