Magnetic Fields and Forces: Key Concepts and Applications
Magnetic Force on a Moving Charge
The magnitude of the force is proportional to the value of the load and the magnitude of the velocity with which it moves. The direction of the force depends on the direction of that velocity.
Helical Path
If the charged particle has a velocity component parallel to the magnetic field and one perpendicular, it follows a helical path.
Conductor Inside a Magnetic Field
The magnetic field interacts with each of the charged particles whose motion produces the current. The force depends on the current, the length of the conductor, and the angle of the conductor with the field.
Magnetic Moment on a Current Loop
Because of the torque, the loop rotates until the vector is oriented in the direction of the field B.
Biot-Savart Law
The value of the magnetic field created by a rectilinear flow at a point is directly proportional to the current intensity and inversely proportional to the distance between the conductor and the point considered.
Magnetic Field in the Center of a Current Loop
In a circular loop, the current element is always perpendicular to the unit vector.
Magnetic Field Created by a Solenoid
A solenoid is a wire wound to form a helix with closely spaced turns. They are like a series of circular loops lying parallel to carry the same current.
Force Between Parallel Currents
The forces that they exert on each other are equal and opposite. There is attraction if the currents flow in the same direction and repulsion if traveling in opposite directions.
Ampere Definition
One ampere is the current that, flowing in the same direction for two very long parallel conductors separated by one meter, produces a mutual attractive force of 2 x 10-7 N per meter of conductor.
- Diamagnetic substances are substances repelled by the magnet.
- Paramagnetic substances are weakly attracted by the magnet.
- Ferromagnetic substances are strongly attracted by the magnet.
Hysteresis Loop
It occurs in ferromagnetic substances. Magnetic hysteresis is the phenomenon that allows the storage of information in magnets and the memory effect. Magnetic losses in electrical machines depend on the surface of the hysteresis loop.
Faraday’s Experiments
Faraday found that in a circuit, the galvanometer indicated the passage of current when the circuit is opened. The same was also true if instead of placing a coil, a magnet was used in motion.
Magnetic Flux
The sense of current to bring the magnet or the field is opposite to the one when it leaves. From static magnetic fields, an electromotive force capable of generating electric current can be induced in a circuit with no connections with any source of power.
Lenz’s Law
The polarity of the induced electromotive force is such that the sense of induced current generates a magnetic field that opposes the change in flow that occurs: The effect is opposed to the cause that provokes it. Whenever the magnetic flow passing through a circuit varies, an emf is induced in it.
Inductance
When a circuit is traversed by a varying current, it produces a changing magnetic flux through it, so there is an emf and induced current.