# Homework Help: Hall probe

1. Jan 30, 2010

### mkbh_10

I place Hall probe b/w two electromagnets and a +ve reading of magnitude of magnetic field is observed , but when i rotate the hall probe , -ve reading is observed on gauss meter . What is happening ??

Also recommend books from where I can study about magneto resistance ,

2. Jan 30, 2010

### !kx!

The hall probe I used contained a semiconductor chip at an end. Current is passed in one direction, and potential difference is measured across another.
Now, you know how a potential difference is generated at right angles to current (magnetic field causes charges to accumulate at either ends, perpendicular to direction of motion). This potential difference is measured, and magnetic field is calculated.

Now, if you turn the hall probe, such that current is still in same direction, then the potential difference measuring terminals will get inverted. However, the charges still tend to move in the same direction as before. This will cause an opposite polarity at the terminals, which now will result into a negative of the previous potential difference, resulting in a negative magnetic field.