Generating Electricity Flashcards
if a magnet is placed near a wire, causing the electrons in the wire to feel a force and move, what is the technical name of this force (other than magnetic force)
electromotive force (emf)
why can the magnetic force be called an emf in this case
- because it is creating / inducing the electric current within the wire
- and emf is a force that results in the creation of electric charge
what can we use this principle to do
generate electricity
how would you induce an alternating current within a wire using this method
by reversing the direction of the magnetic field at set intervals
how does the reversing of the magnetic field induce an alternating current
- it would reverse the direction of the force on the electrons
- therefore reversing the polarity of the emf
- so the electrons would flow in the opposite direction
what does faradays law state
- that the induced emf in a wire is proportional to the rate of change of flux linkage
- in other words, a magnetic field that changes more dramatically will induce a larger emf in the wire
therefore what two things could be practically done to increase the induced emf within a wire
- change the direction of the field at a quicker rate
- or increase the strength of the magnetic field that is changing
- (assuming the time between the change from max value to 0 remains the same)
what does the term magnetic flux linkage mean
- the magnet induces a current within the coil due to its magnetic field
- the current within the coil then produces its own magnetic field because of this
- this would be equal and opposite to the one produced by the magnet
- this is what ‘links’ their magnetic flux
why would the magnetic field produced by the current in the wire be equal and opposite to the magnets field
cuz newtons third law says so
if you were to drop a magnet and stone with the same mass through a copper tube (and the same friction), how would the time in which they come out of the other end compare
the magnetic will take longer to come out of the other end
what is the FALSE reason for this
- that copper is magnetic (it isnt)
- so the magnet is simply attracted to the tube
what law explains what is happening here
lenzs law
what does lenzs law state
- that the direction of an induced emf is such that is opposes the change creating it
- basically the newtons third law shit i mentioned before, but idk about the ‘ equal’ part, just be safe and leave it out i guess
think of the copper tube as a series of copper coils all stacked on top of each other. how does lenzs law explain why the magnet falls through the tube at a slower pace than the rock
- as the magnet falls down, its magnetic field is changing relative to each electron in the tube
- this induces an emf in each copper circlet
- causing a small current to flow around the tube
- the circling current will generate its own electromagnetic field, which will exert an opposite force on the magnet
- top tip, in an exam you should mention how the rock generates no field and so none of this occurs
what is the result of this opposite force exerted on the magnet
- it reduces F in F(resultant) = ma
- as mass isnt changing its reducing its acceleration down the tube
- and therefore reducing the speed of the magnets fall
