# A man moves his head back and forth between the poles of a powerful magnet. He moves...

## Question:

A man moves his head back and forth between the poles of a powerful magnet. He moves perpendicular to the field at a maximum speed of 150 m/s. If he can taste on his tongue, an electric field of 10 V/m, how powerful must the magnetic field be so that he may taste it?

## Motional Electromotive force:

The motional electromotive force is the induced electromotive force by a moving conductor. The induced electromotive force is a potential difference and have the units of volts. The motional electromotive force works at right angles and is proportional to the velocity and length of the conductor.

## Answer and Explanation:

The magnetic field is {eq}0.067 T {/eq}

**Solution:**

The motional electromotive force is

{eq}\epsilon=vBL {/eq}

{eq}\frac{\epsilon}{L}=vB {/eq}

since the units of {eq}\frac{\epsilon}{L}=\frac{[V]}{[m]} {/eq} is the units of the electric field

finding the magnetic field

{eq}B=\frac{\epsilon}{Lv} {/eq}

{eq}B=(\frac{\epsilon}{L})v {/eq}

{eq}B=\frac{10 \frac{V}{m}}{150 \frac{m}{s}} {/eq}

{eq}B=0.067 T {/eq}

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#### Learn more about this topic:

from GACE Physics (530): Practice & Study Guide

Chapter 23 / Lesson 9