Magnetic Fields Flashcards
What is another word for field lines?
Lines of Flux
In what direction do field lines go?
From the north pole to the south pole
How can a magnetic field be induced in a wire?
By moving current through it
What is conventional current?
Current that goes from the positive terminal to the negative
How can you find the direction of the magnetic field around a current-carrying wire?
The right-hand rule.
Thump is current
Fingers travel in the direction of the field
What happens if you place a current-carrying wire in a magnetic field?
It will experience a force that’s perpendicular to the magnetic field and the current
Flemmings left-hand rule?
First finger is Field (index)
seCond finger Current (middle)
Thumb shows you the direction of the force
What happens if the current is parallel to the field lines?
No force
How to determine the force on a current-carrying wire in a magnetic field?
F = BILsinθ
B is flux density
I is current
L is length of the wire
What happens if you put a charged particle in a magnetic field?
A force acts upon it, this is the reason that the force acts on a wire with a current moving through it
How to determine the force that acts on a particle in a magnetic field?
F = Bqvsinθ
B is flux density
q is charge of particle
v is velocity of particle
What is magnetic flux?
Φ = BA
Magnetic Flux = Flux Density * Area
It’s the strength of the field as a collective (total field)
What happens if there is relative motion between a conducting rod and a magnetic field?
The electrons in the rod will experience a force, causing them to accumulate at one end of the rod
Causing p.d (emf) to be induced
How to induce am e.m.f in a solenoid?
Moving the coil away from the poles of the magnet
Moving the magnet towards or away from the coil
Passing a p.d through the coil
What does the size of the emf depend on?
The magnetic flux passing through the coil
the number of turns in the coil
What is the flux linkage?
NΦ = NBA
It is the product of the number of turns and the flux
The Law relating the fluxlinkage, emf and time taken?
Faraday’s law
emf = change in flux linkage / time taken or
ϵ = dNΦ / dt
What law helps to deduce the direction of the induced emf?
Lenz’s Law The induced emf is always in the opposite direction of the of the change that caused it.
RMS p.d?
V / sqrt(2)
Why would a copper disk rotate in the same direction as a plastic disk filled with magnets
Lenz’s law
Copper disk rotates on Same direction to reduce change in flux as it acts to oppose the change that produces it
