Magnetic Fields
Q. Define magnetic field.
A region of space in which moving charged particles are subject to a magnetic force. This force is caused by the interaction of two magnetic fields (there is a field around the moving charged particles which interacts with the existing magnetic field they are passing through).
Q. Are magnetic fields produced by moving charges, permanent magnets or both?
Both moving charges and permanent magnets produce a magnetic field. These fields can interact with one another.
Q. What are magnetic field lines?
Field lines point from North to South. They display the direction of the force on a North pole, if it were moved incrementally around the vicinity of the magnetic field.
Q. How do you represent the strength of a magnetic field on a diagram?
It is represented by how close together the field lines are the closer they are, the stronger the field. (It is the density of field lines per unit area, which is why magnetic flux density and magnetic field strength can be used interchangeably).
Q. What is magnetic flux density?
Magnetic flux density (Magnetic flus per unit area) is equal to the force per unit current, per unit length of a current-carrying conductor, that is placed in a magnetic field, perpendicular to the direction of field lines.
Q. Fleming's left hand rule for motors represents what properties on what fingers?
Thumb = Thrust/Force
First finger = Field (Magnetic)
Second finger = Current
Q. What is the Hall effect?
The Hall effect is the production of a potential difference (Hall voltage) across an electrical conductor induced while it remains in a magnetic field. This potential difference is perpendicular to both the direction of the field and to the direction of conventional current.
Q. What is a Hall probe?
A Hall probe is a device, made up of a copper film of known thickness with a voltmeter across it. When placed in an unknown magnetic field, it ascertains the Hall voltage across the film so that the strength of the field (magnetic flux density) may be calculated.
Q. Describe the motion of a charged particle as it moves through a uniform magnetic field acting perpendicular to its initial velocity.
In the direction of its initial travel, the particle will continue with a constant speed. However, on the perpendicular plane, parallel to the magnetic field lines, positively/negatively charged particles will be accelerated towards the North/South poles respectively. This acceleration changes the direction vector, such that a projectile motion results.
Q. How is a velocity selector oriented?
A velocity selector is comprised of a uniform magnetics and a uniform electric field oriented perpendicularly to one another and an input current oriented perpendicularly to both of these field.
Q. How might you strengthen the magnetic field produced by a solenoid?
Adding a central ferrous iron core within the solenoid strengthens the magnetic field produced. This happens because the core itself becomes magnetised, amplifying the field produced by the solenoid.
Q. Define magnetic flux.
The magnetic flux in area is the product of the magnetic flux density and the cross-sectional area perpendicular to the flux orientation.
Q. What is the magnetic flux linkage?
The magnetic flux linkage of a coil of wire is the number of wire turns multiplied by the magnetic flux produced by a single loop.
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