Magnetism & Electromagnetism Flashcards
Lines of force in space called flux
Magnetic field
The ability of a material to attract iron, cobalt, or nickel
Magnetism
Which way do the lines of flux travel on the inside of a magnet?
On the outside?
South Pole to North Pole
North Pole to South Pole
What happens when the lines of flux travel in the same direction?
Opposite direction?
Repel
Attract
What are magnetic fields distorted by?
What are magnetic fields unaffected by?
Magnetic materials
Non-magnetic materials
What are the 3 laws of magnetism?
- Every magnet has a North and South Pole
- Like poles repel each other and opposite poles attract each other
- Inverse square law
What are the 4 categories of magnetic properties?
Nonmagnetic
Diamagnetic
Paramagnetic
Ferromagnetic
Not attracted to magnetic fields (glass, wood, plastic)
Nonmagnetic
Repelled by magnetic field (water, mercury, gold)
Diamagnetic
Feebly attracted to magnetic fields (platinum, gadolinium)
Paramagnetic
Strongly attracted to magnetic fields (iron, cobalt, nickel)
Ferromagnetic
Electricity and magnetism forces
Electromagnetism
What are the 3 main types of magnets?
Natural magnets
Artificial/Permanent magnets
Electromagnets
Example: Refrigerator magnet
Artificial/permanent magnet
Is only a magnet when electricity is flowing through it
Electromagnet
What is the SI unit of magnetic field strength?
Tesla
What are some other ways to say ‘magnetic fields’?
Zone of influence
Lines of force
Magnetic flux
The more closely spaced magnetic fields are, what happens to them?
They become stronger
What creates a magnetic field?
Electricity
The branch of physics that deals with the relationship between electricity and magnetism
Electromagnetism
Which experiment demonstrates Lines of Force?
Davy’s
When does a magnetic field exist around a wire?
When there is an electric current flowing
What is another name for electromotive force?
Electric potential
Higher voltage the higher potential to do work
Electrical potential
A device that converts some form of energy directly into electric energy is said to be a source of _____.
Electromotive force (EMF)
A coiled wire (helix)
Solenoid
What will further intensify a magnetic field?
Inserting a magnetic material (iron) within solenoid
Can magnetic field generate electricity?
Under certain conditions
What is the first law of electromagnetic induction?
A moving magnetic field can create an electric current
What happens when a wire is cut across the lines of a magnetic field?
Electricity is induced
Which 4 factors determine induced electromotive force?
Speed
Strength
Angle
# of turns
What are the 3 ways to induce an electromotive force,or voltage, in a wire?
- The wire may move across a stationary magnetic flux
- The magnetic flux may move across a stationary wire
- The magnetic flux may vary in strength while a stationary wire lies in it
What is the diagnostic range for kVp?
30-150
What is the 2nd law electromagnetic induction?
The induced current will flow in the opposite direction of the action that induces it
What are the 2 types of induction?
Self-induction
Mutual induction
Process by which the magnetic field of a coil induces a counter EMF in the coil itself
Self-Induction
Which type of induction uses autotransformers?
Self-Induction
Inducing a current flow through the secondary coil by passing a changing current through the primary coil
Mutual induction
True or false. The first coil is always the primary coil.
True
Electrical energy to mechanical energy
Electrical motors
Mechanical energy to electrical energy
Generators
What is essential to electromagnetic induction?
The intensity of the magnetic field at the coil must be changing to induce a current flow
A device that changes an alternating current from low-voltage to high-voltage or from high-voltage to low-voltage
Transformers
Are Transformers 100% effective?
Not normally.
Usually 90%-95%
More turns in secondary coil than in primary coil
Step-up transformer
Fewer turns in secondary coil than in primary coil
Step-down transformer
If you increase the # of turns, what happens to voltage?
What happens to amperage?
Voltage increases
Amperage decreases
If you decrease number of turns, what happens to voltage?
What happens to amperage?
Voltage decreases
Amperage increases
What are the three types of transformers?
Closed core
Shell type
Autotransformer
What are the 3 types of energy losses?
Resistance
Hysteresis
Eddy Currents
