Chapter 20 Flashcards
What is magnetism?
Magnetism is a phenomenon by which certain materials exert attractive or repulsive forces on other materials.
What is a magnetic field?
A magnetic field is the region of space where magnetic forces may be felt.
What is a magnetic field line?
A magnetic field line is the line along which a north pole would move if free to do so.
What is magnetic flux density?
Magnetic flux density is a measure of the strength of a magnetic field
What is an ampere?
The Ampere (A) is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible cross-section, placed one metre apart in a vacuum, would produce a force on each conductor of newtons per metre length
What is magnetic declination?
The angle between true north and magnetic north at a point on the Earth
What is electromagnetic induction?
Electromagnetic induction is where an emf is induced by a change in the magnetic flux linking a circuit.
What is magnetic flux?
Magnetic flux is the total amount of magnetic field in a given region; it is the product of magnetic flux density and area.
State Faraday’s Law
Faraday’s Law (of electromagnetic induction) states that the magnitude of an induced emf is proportional to the rate of change of flux linking a circuit.
State Lenz’s Law
The direction of the induced emf is always such as to oppose the change causing it.
What is alternating current?
An alternating current is an electric current whose direction changes periodically.
What is mutual induction?
Mutual induction is where a changing magnetic field in one coil induces an emf in another coil.
What is a transformer?
A transformer is an electrical device used to change the voltage of a.c. power supplies.
What is self-induction?
Self induction is where a changing magnetic field in a coil induces an emf in the coil itself.
What is an inductor?
An inductor is a device used to induce a back emf.
