# Give your comments on the statement that “Magnetic fields exert a force on all moving electrically charged particles”. If yes explain it, if not prove it.

valentin68 | College Teacher | (Level 3) Associate Educator

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The statement is true. Two simple explanations follows below.

1. By definition in physics the magnetic field is the field generated by moving electrical charges. Since an electric charge that moves creates a magnetic field, this field will interact with any other external magnetic field (two magnets repels or attract each other). Therefore the external magnetic field will exert a force on all moving electrically charged particles (by the field-field interaction).

2. In physics the Lorentz force is the force exerted by a magnetic field of induction on a moving charge q, having speed v. The expression of this force is

F=q*(V  x  B)

where F, V, B are vectors and x is the vectorial product. In absolute value

`F= q*v*B*sin(/_(V, B))`

The direction of this force is drawn in the figure below.

This Lorentz force is used in physics as a second way to define the magnetic field. Thus the magnetic field is a field that interacts with any moving electrical charge in the sense described above.

Observation:

There is a single case when the force exerted by a magnetic field on a moving electrical charge is null. This happens (as can be seen from the above definitions) when the magnetic field B and the speed of particle V are parallel.

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