What is the net magnetic force on a compass needle? By what mechanism does a compass needle line up with a magnetic feild?
(B) is typically measured in either teslas (SI units) or gauss (cgs units), while the magnetic field intensity (H) is measured in Amperes/meter (SI units) or oersted (cgs units).
First, changes in either of these fields can cause ("induce") changes in the other, according to Maxwell's equations. Second according to Einstein's theory of special relativity, a magnetic force in one inertial frame of reference may be an electric force in another, or vice-versa (see relativistic electromagnetism for examples). Together, these two fields make up the electromagnetic field, which is best known for underlying light and other electromagnetic waves.
The net magnetic force on a compass needle is the vector sum of all the magnetic forces acting on it. It is the force that determines the direction in which the needle aligns itself with a magnetic field.
To understand how a compass needle aligns itself with a magnetic field, we need to consider the mechanism of magnetic force. The basic principle involved is that a magnet, like the Earth's magnetic field, exerts a force on a magnetic material, such as the needle of a compass. This force is a result of the interaction between the magnetic field and the magnetic dipole moment of the compass needle.
The magnetic dipole moment is a property of the compass needle caused by the alignment of its atomic or molecular magnetic moments. When a compass needle is placed near a magnetic field, the magnetic field exerts a torque on the dipole moment of the needle, causing it to rotate. The needle aligns itself such that its magnetic dipole moment is parallel to the magnetic field lines. This alignment reduces the potential energy of the system, as the dipole aligns with the field, resulting in a stable equilibrium position.
The net magnetic force acting on the compass needle can be calculated using the equation:
F = m * B * sin(θ)
where F is the magnetic force, m is the magnetic dipole moment of the needle, B is the magnetic field strength, and θ is the angle between the needle and the magnetic field.
So, to determine the net magnetic force on a compass needle, you need to know the magnetic field strength and the angle between the needle and the magnetic field. With this information, you can calculate the force using the above equation.