Chapter 14 - Magnets and Electromagnetism Flashcards
What is the relationship between the magnetic force and distance?
The magnetic force between two poles decreases with
the square of the distance between the two poles
What does magnetic dipole mean?
A magnet always has at least two poles
What did Oersted discover?
That a compass needle was deflected by a current-carrying wire
How does the direction of the current give you the direction of the magnetic field produced?
The magnetic field produced by the current is
perpendicular to the direction of the current
What happens when two current-carrying wires in parallel have current flowing in the same direction?
They exert an attractive force on each other
What are the units for Magnetic field (magnetic flux density)?
1 Tesla (T) = 1 N(Am)^-1
What is the equation for magnetic field?
B = F / qv
For this relationship to be valid, the velocity must be
perpendicular to the field
How do you determine the direction of a magnetic force?
If the index finger of the right hand points in the direction of the velocity of the charge, and the middle finger in the direction of the magnetic field, then the
thumb indicates the direction of the magnetic
force acting on a positive charge
Why does the force do no work on a moving positively charged particle?
- The force is perpendicular to the velocity of the particle, the force does no work on the particle
- It cannot increase the particle’s kinetic energy; it only changes the direction of the particle’s motion (centripetal acceleration)
What happens when a current-carrying wire is bent into a circular loop?
The magnetic fields produced by different segments of the wire add to produce a strong field near the centre of the loop
What is the magnetic field produced by a current
loop identical to?
Identical to one produced by a short bar magnet
What is Faraday’s Law?
A voltage is induced in a circuit when there is a change in magnetic flux passing through the circuit
What is the induced voltage equal to?
- The rate of change of magnetic flux
- This process is called electromagnetic inductance
What is magnetic flux?
A measure of how much magnetic field is passing through a loop of wire
What is Lenz’s Law?
The direction of the induced current generated by a change in magnetic flux produces a magnetic field that opposes the change in the original magnetic flux
