How to find the magnitude of magnetic field in simplest form?
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There's a magnetic field and you need to measure its strength. But how? Here are some options.
Back when I was a kid, we had these things called compasses. It's just a magnetic needle inside a case that is free to rotate. Since a magnetic field can exert a torque on another magnet, this needle will line up in the direction of the net magnetic field. What is a compass used for? Well, it just so happens that the Earth creates a magnetic field that is mostly constant at a given location. The compass can then be used to determine direction. Here is the cool part, the compass even works underwater (try that with your phone - actually, you probably shouldn't).
The compass doesn't give you the value of the net magnetic field, just the direction. So, how do you get the magnitude of a particular field from this? The trick is to assume the value of the Earth's magnetic field and the direction of the compass. Let's assume that at this location on the Earth, the magnetic field is pointing directly North with a horizontal component of about 2 x 10-5 T.
Now suppose that I do something to create a magnetic field in a known direction and perpendicular to the horizontal component of the Earth's magnetic field. Here is an example where I put a current carrying wire right over the compass needle. Since the compass is underneath the wire, the magnetic field due to the wire will be 90° to the Earth's magnetic field.
Back when I was a kid, we had these things called compasses. It's just a magnetic needle inside a case that is free to rotate. Since a magnetic field can exert a torque on another magnet, this needle will line up in the direction of the net magnetic field. What is a compass used for? Well, it just so happens that the Earth creates a magnetic field that is mostly constant at a given location. The compass can then be used to determine direction. Here is the cool part, the compass even works underwater (try that with your phone - actually, you probably shouldn't).
The compass doesn't give you the value of the net magnetic field, just the direction. So, how do you get the magnitude of a particular field from this? The trick is to assume the value of the Earth's magnetic field and the direction of the compass. Let's assume that at this location on the Earth, the magnetic field is pointing directly North with a horizontal component of about 2 x 10-5 T.
Now suppose that I do something to create a magnetic field in a known direction and perpendicular to the horizontal component of the Earth's magnetic field. Here is an example where I put a current carrying wire right over the compass needle. Since the compass is underneath the wire, the magnetic field due to the wire will be 90° to the Earth's magnetic field.
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Back when our fathers were a kid, they had these things called compasses. It's just a magnetic needle inside a case that is free to rotate. Since a magnetic field can exert a torque on another magnet, this needle will line up in the direction of the net magnetic field. What is a compass used for? Well, it just so happens that the Earth creates a magnetic field that is mostly constant at a given location. The compass can then be used to determine direction. Here is the cool part, the compass even works underwater (try that with your phone - actually, you probably shouldn't).
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