# Homework Help: Hall Probe Problem

1. May 7, 2005

### medusa

there are two permamnent bar magnets put with a south pole facing a north pole.
there is a magnetic field in between the bar magnets.
i need to use the hall probe to measure the field strentgh.
the probe measures a hall voltage and i can convert this to magnetic field strength values using the calibration graph i have.

the problem i have is that i think current must flow through the hall probe so to excite the electrons so they can be deflected once the probe is in the field. otherwise i will not be able to get any hall voltage reading.
can someone explain to me that should there be current flowing through the hall probe? for me to get hall voltage readings or can i just place the hall probe in the field without any current flowing through the probe? and it just bieng connected to a voltmeter.

2. May 7, 2005

### ZapperZ

Staff Emeritus
For the magnetic field to act on the charge carriers in the Hall probe, the carriers must be moving. If not, the v x B term in the Lorentz force will be zero and nothing interesting will occur. And to make the charge carriers move, you have to supply a potential difference to cause a current to flow.

Zz.

3. May 7, 2005

### medusa

ok
to calibrate the probe i will be using a solenoid. so there must be current flowing through the solenoid to cause a magneic field and also current flowing through the probe to cause movement of the electrons.
but the current in the probe should be small and steady? as it is only required to cause movement of the electrons.

from this link you can see they are calibrating the probe but no mention of any current flowing through the probe.

http://dept.physics.upenn.edu/~uglabs/lab_manual/magnetic_field.pdf

4. May 7, 2005

### ZapperZ

Staff Emeritus
Humm... is it possible that there are Hall Probes that don't need to be attached to a power supply? I'm trying to think.....

It is possible that all you need to do is set it to a particular current value and leave it at that for your calibration and measurement. The manufacturer may also provide the working settings.

Now, are you sure that these Hall probes do not have any batteries in them?

Zz.

5. May 7, 2005

### medusa

ok i will try to find and see what settings the manufacturers give.

6. May 7, 2005

### medusa

they give no current rating.
im sure without current no charge will flow.
but to calibrate it should constant current be passed through the probe?
like you could make a steady current of 1,2 or 3 amps to flow etc.
but this has an effect on the hall voltage therefore the it is not accurately calibrated.

7. May 7, 2005

### ZapperZ

Staff Emeritus