Magnetic Fields Flashcards
In Fleming’s Left Hand Rule, what does each finger represent?
First finger = Field, Second Finger = Conventional Current, Thumb = Thrust or Motion.
What is the equation symbol for magnetic flux density and what is it measured in?
The symbol is B and it is measured in Tesla (T).
What does 1T represent?
A wire carrying a current of 1A placed perpendicular to a magnetic field experiences 1N of force per metre of its length.
What is the difference between the equations F=BIL and F=BQv?
The first equation refers to the current in a wire while the second equation refers to a single moving charge carrier.
How do you calculate magnetic flux?
Multiply the magnetic flux density by the area of the surface in the magnetic field and the sin of the angle between the field and the surface.
What is the magnetic flux linkage?
The product of the magnetic flux and the number of turns in the coil of wire.
How is an e.m.f induced in a circuit by magnets?
An e.m.f is induced whenever there is a change in the magnetic flux linking the circuit.
What is Faraday’s Law?
The magnitude of an induced e.m.f is directly proportional to the rate of change of the magnetic flux linkage.
What is Lenz’s Law?
The direction of an induced e.m.f is always opposite to the direction of movement of the charge producing it. (Think magnet in metal tube)
How does a transformer work?
1) An alternating current in the primary coil causes an alternating magnetic flux.
2) The iron core links the flux to the secondary coil.
3) The changing flux linkage in the secondary coil induces an e.m.f in the wire, creating a current.
What are two ways to make a transformer more efficient?
Using low resistance wires reduces power losses due to the wire heating up and laminating layers in the iron core stops eddy currents from forming.
What causes a magnetic field?
Permanent magnets or moving charges.
What direction do magnetic field lines point?
Positive to negative.
Why do moving charged particles in magnetic fields move in circular paths?
The force acting on them is always perpendicular to their direction of motion.
In both a magnetic field and an electric field, what must happen for a particle to be undeflected?
Its electric force (EQ) must equal its magnetic force (BQv).
