# How can magnetic force be reduced?

Dec 4, 2015

Reduce the magnetic field the object is in, reduce the charge of the object, reduce the speed of the object, or change the direction the object is traveling - as the angle between velocity vector and magnetic field approaches zero, so will the magnetic force on the object.

#### Explanation:

There are lots of ways to reduce magnetic force on something depending on the context, so it's important to think hard and analyze the situation.

Just as a demonstration let us consider a simple system of one charged object traveling at constant velocity through a uniform magnetic field. The object has a charge of $q$ and is traveling with a velocity of $\overline{v}$. (the bar indicates a vector)

The force experienced by the object due to the magnetic field will be

${F}_{\text{mag}} = q \overline{v} \times \overline{B} = q v B \sin \theta$

where $\overline{B}$ is the magnetic field through which the object is traveling, and "$\times$" is the cross product. $\theta$ then is the angle between the magnetic field and the object's velocity.

So according to this equation, it should be easy to see that there are a few different ways we could reduce the magnetic force: decrease the charge of the object, decrease the speed of the object, decrease the strength of the magnetic field through which the object is traveling, or change the angle between the magnetic field and the object's velocity vector such that they are parallel - in other words, cause $\sin \theta$ to be zero.

I hope that helps. There are other possible scenarios where you might have a second moving charged particle generating the magnetic field - in that case you could find the magnetic field vector via Biot-Savart and analyze how that could be reduced, hence reducing the force on the other object. But I'll leave that to you as an exercise.. the scenario I presented above is the basic answer.