Chapter 15 Flashcards
What does the right hand rule describe?
The direction of a magnetic field around a current-carrying wire.
What happens if you put a current-carrying wire into an external magnetic field?
Field around the wire and field from the magnets interact causing the field lines from the magnet to contract and form a “stretched catapult” effect.
Equation for the size of the force on a current-carrying wire
F = BIL
Equation for permeance
ϕ = ΛNI
Flux is maximized by:
- Large area of cross section
- Small air gaps
- Large N and I
Equation for permeance and permeability
Λ = μA/L
What do flux lines tend to do?
Tend to contract.
What is magnetic field strength/flux density?
Measures the strength of the magnet per unit area.
What can flux be thought of as?
Total number of field lines.
What happens when a conducting rod moves through a magnetic field?
Its electrons will experience a force meaning that they will accumulate at one end of the rod, thus inducing an emf across the rods as a battery would.
If this rod is part of a complete circuit, then a current is induced.
When is e.m.f induced?
Whenever there is relative motion between a conductor and a magnet.
Whenever flux lines are cut.
Under what condition will an induced emf also induce a current?
If the circuit is complete.
What does Lenz’s Law state?
The induced e.m.f is always in such a direction as to oppose the change that caused it.
What is the force on a moving charge?
F = qvB (sin 0)
In what way can the coils of a transformer be altered to increase efficiency?
Conductance of the copper coils need to be high to limit energy loss.
