# How can I measure the actual magnetic strength of my electromagnet to compare against my calculations?

I am interested in building small scale electromagnets and I wanted to measure their actual magnetic strengths to compare against my calculations. What are possible ways to measure the difference?

• Questions seeking recommendations for particular products are off-topic here. – Hearth May 15 at 14:44
• As it stands, this could be closed as off topic for asking for product recommendations. If you were to edit the question, to ask about methods of measuring magnetic strength and what you want to measure (field strength, pull strength etc), and not ask for particular brands, then this may be an answerable question. You would need to show what you have researched first and what methods you have thought of. HINT: A good place to start is Hall effect and Magnetoresistance – MCG May 15 at 14:46
• ogginger, Measure the magnetic strength of a magnet by using a compass. Keep the magnet far away, at first, and let the compass settle. Orient your magnet so that its poles point at the compass and you are coming from the west towards the compass. If you get the N pole pointed at the compass, then as you approach the N-vane of the compass will move away from the magnet as you get closer. Do this until you see the N-vane is 45 degrees or more away from its natural position and measure the distance to the compass. The deflection angle and the Earth's magnetic field at your location is enough. – jonk May 15 at 18:10
• If you want to re-open the question, re-write it so that it doesn't ask for brands or models but instead asks for a procedure to follow with common parts and I'll write up a fuller explanation and a detailed procedure to follow. But the essence of the question is: $\vec{B}_\text{net}=\vec{B}_\text{Earth}+\vec{B}_\text{magnet}$. From that, all can be computed. – jonk May 15 at 18:12
• Hmm. I've never tried to answer a question that's on hold. But set up the compass as described above. Move the magnet towards the compass along a line perpendicular to the magnetic N-S line at your location. Do this until you observe a 70-degree angle on the compass, relative to the N-S line. Stop. Measure distance from magnet to center of compass in meters. Cube this value and multiply by 275 (most of US, but not all.) That will be in units of $A\cdot m^2$. For example, if the distance away was $20\:\text{cm}$, the dipole moment of the magnet is $2.2\:\text{A}\cdot\text{m}^2$. – jonk May 16 at 5:38