Chapter 4 Flashcards
What is the fundamental force associated with magnetism?
The ability to attract iron due to the motion of charged atomic particles.
What are the two types of magnetic moments?
- Orbital magnetic moment
- Spin magnetic moment
Define magnetic dipoles or magnetic domains.
Groups of atoms with their net magnetic field moving in the same direction.
What is the SI unit for magnetic flux?
Weber (Wb)
How do lines of force behave in relation to each other?
Lines of force NEVER intersect.
What is the direction of magnetic field lines outside and inside a magnet?
Outside: North to South; Inside: South to North.
What is flux density measured in?
Tesla (T) and Gauss (G).
What are the classifications of magnets?
- Natural
- Artificial permanent
- Electromagnets
According to the laws of magnetism, what happens with like and unlike poles?
Like poles repel; unlike poles attract.
What does the inverse square law state in magnetism?
The force between two magnetic fields is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them.
What is magnetic induction?
The alignment of dipoles in a non-magnetized iron bar when brought within the lines of force of a strong magnet.
What are the two general characteristics of materials regarding magnetism?
- Permeability
- Retentivity
What are ferromagnetic materials?
Materials that are highly permeable and susceptible to induction (e.g., iron, cobalt, nickel).
What is Oersted’s experiment known for demonstrating?
The relationship between a moving electric charge and magnetism.
What do Fleming’s Hand Rules assist with?
Understanding the relationship between electricity and magnetism.
What is a solenoid?
A coil consisting of a series of loops to increase flux density.
What are the required components for electromagnetic induction?
- Magnetic field
- Conductor
- Relative motion
What does Faraday’s Law state?
Four factors regulate the strength of induced current when magnetic lines of force and a conductor are in motion relative to each other.
What is Lenz’s Law?
Induced current flow sets up a magnetic field opposing the action that produced the original current.
What is mutual induction?
The result of two coils being placed in close proximity with a varying current supplied to the first coil, inducing a similar flow in the second coil.
What is self-induction?
The ability of an alternating current to switch directions, causing an opposing potential difference to induce against the incoming supply of electrons.
What do generators do?
Convert mechanical energy to electrical energy.
What is the purpose of the thumb rule in Fleming’s Right-Hand Generator Rule?
Thumb points in the direction of moving wire.
What is the primary purpose of transformers?
To change voltage levels in electrical circuits.
What are the two types of transformer loss?
- Copper loss
- Hysteresis loss
- Eddy current loss
What is the difference between a step-up and step-down transformer?
- Step-up: Increases voltage
- Step-down: Decreases voltage
What is the basic function of capacitors?
To accumulate and store electrical charge.
What does rectification refer to?
The process of changing AC to DC.
What is half-wave rectification?
Produces a DC waveform similar to self-rectification using a single rectifier.
What is full-wave rectification?
Uses at least four rectifiers in a bridge rectification circuit to provide only DC to the x-ray tube.
What is thermionic emission?
The process of liberating electrons from a heated wire filament.
What does the term ‘inductive reactance’ refer to?
The ability of an alternating current to switch directions, causing opposing potential difference.
What types of motors are classified as synchronous AC?
Coils turn at the same rate as the armature supplying current.
What is the main difference between DC and AC motors?
DC motors use commutator rings; AC motors use slip rings.
What is the smallest quantity of any type of electromagnetic radiation
photon
What is the velocity of all electromagnetic radiation?
3 × 10^8 m/s
What rate of rise and fall of a sine wave is called?
frequency
How many cycles per second in a hertz?
one
What is the electromagnetic wave equation?
c = fλ
What produces a magnetic field?
electric charges in motion.
The radiation intensity _________ in ___ proportion to the object’s squared distance from the source.
decreases
inverse
As an item becomes farther away, the radiation’s intensity decreases because the radiation ___________.
is spread out over a greater area
A photon’s _____ is exactly proportional to its energy.
frequency
Typically, X-rays can be recognized by their __________?
energy
Matter __ their wavelength tends to interact with photons.
equal in size to
The flux of magnetic energy in a wire loop
is maximum when the plane of the loop is perpendicular to the magnetic field.
In a wire loop, an induced current
results from an alernately expanding and contracting magnetic field
What is the process of electrons being emitted from heated metallic surfaces called
thermionic emission
A transformer with more secondary windings than primary windings
has a greater secondary voltage
In a minute, how many times does an AC current change direction?
7200
American generators operate at
60 hz
Where in the x-ray circuit is the rectifaction circuit found?
between the step up transformer and the x-ray tube
A diode electron tube such as a valve tube
can be used for rectifaction
What is a stator?
electromagnets
