Measuring magnetic flux density using a Hall probe
- A Hall probe can be used to measure the magnetic flux density between two magnets based on the Hall effect
- It consists of a cylinder with a flat surface at the end
Hall probe
A Hall probe consists of a flat surface and is held so the magnetic field lines are perpendicular to it
- To measure the magnetic flux density between two magnets, the flat surface of the probe must be directed between the magnets
- This is to ensure the magnetic field lines pass completely perpendicular to this surface
Hall probe in a magnetic field
The Hall probe creates a Hall voltage when placed in a magnetic field
- The probe is connected to a voltmeter to measure the Hall voltage
- If the probe is not held in the correct orientation (perpendicular to the field lines), the voltmeter reading will be reduced
- Since the Hall voltage is directly proportional to the magnetic flux density, the flux density of the magnets can be obtained
- A Hall probe is sensitive enough to measure even the Earth’s magnetic flux density
Worked example
A Hall probe is placed near one end of a solenoid, as shown in the diagram.
The Hall probe is rotated about the axis XY.
State and explain why the magnitude of the Hall voltage varies.
Answer:
- The Hall voltage depends on the angle between the magnetic field and the plane of the probe
- The Hall voltage reaches a maximum when the field is perpendicular to the probe
- The Hall voltage is zero when the field is parallel to the probe
