Electric fields Flashcards
Electric field lines go from _ to _
positive to negative
Direction of electric field
force that a positive charge would experience - perpendicular to magnetic field
Electron will experience force in:
opposite direction to electric field
Magnetic flux is a maximum when:
Perpendicular to magnetic field (magnetic field is 90 degrees and flux is 0)
The angle of magnetic flux is:
the normal to the area and direction of field
What induces an EMF
Magnetic field induces EMF, and thus current since EMF is a voltage
How is an EMF produced?
As charges move apart, due to the force from the magnetic field, one end of the object will become more positive and the other end will be more negative.
This creates a potential difference, (EMF)
3 factors that induce an EMF
- Change in magnetic field
- Changing area perpendicular to magnetic field
- Changing angle through which the magnetic field lines pass
Faster the change in magnetic flux,
greater the EMF
How does a transformer work
Works on the basis of a changing current in the primary coil inducing a change in magnetic field and thus, a changing magnetic field which in turn induces a current in the secondary coil
Changing magnetic flux is directed to the secondary coil where it will induce an EMF in that coil
Lenz’s law
An approaching magnet will induce a current that will induce a magnetic field that opposes the original magnet’s magnetic field
A magnet falling through an aluminium pipe, for example, will induce a current in the pipe which then induces a magnetic field in the opposite direction to the magnet, thus slowing it down.
When will an electron possess potential energy?
When held from a charge. WHen released, this potential turns into KE
What is the direction of an induced current (electromagnetic induction)
It is in a direction such that it opposes the changing flux
This is so the law of conversation of energy is maintained - if it did not oppose the flux, energy would be endlessly created
When a magnet is leaving a wire, does the induced current repel or attract the magnet?
It attracts. This is to oppose the change in motion - the magnet is moving away which means the current must go in the opposite way in order to counter the movement. Because the magnet is moving away, current opposes this motion which means the magnetic field is in such a way that it attracts the wire.
How is electromagnetic radiation propagated?
Propagates through mutually perpendicular magnetic fields and electric fields (they are perpendicular to each other) that oscillate.
