Magnetic fields Flashcards
(9 cards)
Describe what the student would observe on the ammeter as the magnet falls through the coil
The magnetic field increases as the magnet falls into the coil, an e.m.f is induced hence the reading on the ammeter deflects one way. AS the magnet leaves the coil the magnetic field decreases hence the reading on the ammeter deflects the opposite way.
Faraday’s Law
The magnitude of the induced e.m.f is directly proportional to the rate of change in magnetic flux linkage
Lenz’s Law
The direction of the induced e.m.f when there is a change of flux linkage is such that it will try to oppose the change of flux that is producing it.
State the condition in which F= BIl applies
I must be parallel to B
Len’z law can be demonstrated using a bar magnet and a coil of wire connected to a sensitive ammeter. The bar magnet is moved towards the coil and is then brought to a halt. State how the reading on the ammeter changes during this process.
The reading shows dc current flow which then becomes zero when the magnet stops using.
A search coil is moved at a constant speed along the axis so that x is increasing. An emf is induced across the terminals of the search coil.
Explain what happens to the value of the emf as the search coil moves.
As the coil moves there is a rate of change of flux through the coil as emf= N (delta BA)/(delta t).
The induced emf is proportional to the rate of change of flux linkage so the magnitude of emf decreases.
Explain why the proton travels in a semi circular path in a dee
Force due to uniform magnetic field is constant and always at 90 degrees to the direction of travel. This force is centripetal.
WORK DONE= KINETIC ENERGY
not a question j remember it dummy
An alternating emf is induced in a coil rotating in a magnetic field.
What is the phase difference between the magnetic flux linkage through the coil and the emf?
pi/2 rad
