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Radiologic Physics > Test 2 > Flashcards

Test 2 Flashcards

0
Q

Insulator

A

Any material that doesn’t allow electron flow
Confine the electron flow to the conductor
Can be touched
Glass clay wood earth like materials

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1
Q

Conductor

A 
Any substance through which electrons flow easily 
Most metals are conductors
Copper aluminum silver 
Water 
If touched can result in a shock
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2
Q

Semiconductor

A

A material that in some condition behaves as an insulator and in other conditions behaves as a conductor
Silicon germanium

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3
Q

Superconductor

A

Materials that conduct electrons with zero resistance when they’re cooled to a very low temperature

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4
Q

4 factors that effect the flow of electrons that increase or decrease resistance

A

1 ability to conduct electrons
2 length of the conductor
3 cross sectional diameter
4 temperature

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5
Q

1 ability to conduct electrons

A

Conductor permits electrons to flow easily
Decreases resistance
Insulator inhibited the movement of electrons
Increases resistance

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6
Q

2 length of the conductor

A

The length is directly proportional to resistance
If length of the conductor doubles the resistance doubles
The longer the conductor the greater the resistance

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7
Q

3 diameter of conductor

A

Diameter is inversely proportional to the resistance
As the diameter doubles the resistance will be cut in half
Larger the diameter the less resistance

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8
Q

4 temperature

A

Inverse relationship
As temp increases the flow of electrical current
as temp rises electron flow decreases

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9
Q

Series circuit

A

All circuit elements are connected in a line along the same conductor

Ex: Christmas lights

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10
Q

Rule #1 series circuit resistance

A

Total resistance is equal to the sum of the individual resistance
Rt=R1+R2+R3

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11
Q

Rule #2 series circuit current

A

The current through each circuit element is the same and is equal to the total circuit current
Current is same throughout

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12
Q

Rule #3 series circuit voltage

A

The sum of the voltages across each circuit element is equal to the total circuit voltage

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13
Q

Parallel circuit

A

Contains elements that are connected at their end rather than lie in a line along a conductor
Divided among several branches or pats following simultaneously

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14
Q

Rule #1 parallel circuit current

A

The sum of the currents through each circuit element is equal to the total circuit current
It=I1+I2+I3

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15
Q

Rule #2 parallel circuit voltage

A

The voltage across each circuit element is the same and is equal to the total circuit voltage

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16
Q

Rule #3 parallel circuit resistance

A

The total resistance is the inverse of the sum of the reciprocals of eac individual resistance
1/RT=1/R1+1/R2+1/R3

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17
Q

What are the 3 ways objects can be electrified

A

1 friction
2 contact
3 induction

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18
Q

1 friction

A

Occurs when one object is rubbed against another

Electrons travel from one to the other

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19
Q

2 contact

A

Occurs when 2 objects touch permitting electrons to move from one to the other
Simply an equalization of Charges

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20
Q

3 induction

A

Most important
The process of electrical fields acting on one another without contact
When a strong and weak charged object come close to one another the electrical fields begin to act on one another

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21
Q

What are 3 ways to induce an EMF

A

1 move the wire
2 move the magnet
3 vary strength of magnetic field

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22
Q

The magnitude of an induced EMF depends on

A

1 velocity of magnetic field as it moves past the conductor
2 the strength of the magnetic field
3 the angle of the conductor to the magnetic field
4 the number of turns in the conductor

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23
Q

1 velocity of magnetic field

A

The faster it turns increases the EMF

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24
Q

2 strength

A

Te stronger the magnet the more current

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25
Q

3 angle

A

The more flux lines it cuts the stronger the current

26
Q

4 number of turns in conductor

A

The more coils the stronger the induced current

27
Q

Electric potential

A

If electric charges are positioned close to each other they have electric potential energy
When electrons are clustered at an end of a wire they Create an electric potential because the electrostatic repulsive force causes some electrons to move along the wire and work can be done
Voltage, potential energy and potential difference are the same thing

28
Q

Current

A

The quantity or number of electrons flowing
Amount of electrons burning off= current or amperage
Unit is the ampere
Symbol is I
Coulombs per kilogram

29
Q

Voltage

A

Joule per coulomb
Amount of energy per unit of charge
10 volts = 10000 kV

30
Q

Resistance

A

The opposition to the flow off current

31
Q

Ohms law

A

Voltage = current * resistance
V=IR
Use the triangle

32
Q

3 formulas for power

A 
1 P= IV 
Power = current (amps) * voltage 
2 P = I squared R 
Power = current * current * resistance 
3 P= V^2 / R
33
Q

Anmeter

A

When a meter is connected in series it measures current in amperes
Connected directly into the circuit
Used in series circuit
Measures the quantity (amperage) of electric charge flowing per second

34
Q

Voltmeter

A

When a meter is connected in parallel it measures potential difference in volts
Used in parallel circuit
Measures the pressure in the circuit where there’s high resistance

35
Q

Coulomb’s law

A

The electrostatic force is directly proportional to the product of the electrostatic charges and is inversely proportional to the square of the distance between them
The electrostatic force is very strong when objects are close but decreases quickly as objects separate

36
Q

Power

A

P= IV
Power = current (amps) * voltage
Measured in watts

37
Q

Left hand thumb rule

A

If a wire is grasped in the left hand with the thumb pointing in the direction of the electron flow (- to +) then the fingers encircling the wire indicate the direction of the magnetic field lines around the current

38
Q

Electric current

A

Goes from positive to negative

39
Q

Electron flow

A

Goes from negative to positive

40
Q

Direct current

A

All electrons move in the same direction

Provided by 2 wires connecting the equipment to a power source

41
Q

Alternating current

A

All electrons move first in one direction and then reverse and move in the opposite direction
Can do more with this current happens 60 times a second

42
Q

Is it possible to change the current from DC to AC an back?

A

Yes

43
Q

Electrical circuit

A

A pathway that permits electrons to move in a complete circle

44
Q

Circuit breaker

A

An electromechanical device which interrupts the circuit when excess current is drawn over its rating
Protects from too much electricity

45
Q

Fuses

A

Protects from too much electricity
Contains a metal tab that melts to break the circuit
Not reusable

46
Q

Self induction

A

When you change the current in a coil off wire the magnetic field it produces will change. This will change the magnetic flux through the coil and produce a voltage across the coil
One coil

47
Q

Mutual induction

A

2 coils are placed in proximity and a varying current supplied to the first coil induces a similar flow in the second coil

48
Q

Electromagnets

A

Temporary magnet because it only works when electricity is running through it

49
Q

Non magnetic

A

Unaffected by a magnetic field

Wood glass plastic

50
Q

Diamagnetic

A

Materials are weakly repelled by all magnetic fields

Bismuth lead

51
Q

Paramagnetic

A

Materials lie somewhere in the middle of ferromagnetic and non magnetic
Weakly attracted to a magnet and loosely influenced by an external magnetic field
Platinum contrast agents

52
Q

Ferromagnetic

A

Materials are strongly attracted by a magnet
Can usually be permanently magnetized
Strongest

53
Q

5 magnetic laws

A 
1 dipoles 
2 magnetic poles 
3 repulsion/attraction 
4 inverse square law 
5 magnetic induction
54
Q

1 dipoles

A

Dividing a magnet simply creates 2 smaller magnet having as north and South Pole

55
Q

2 magnetic poles

A

No matter how much a magnet is divided both poles continue to exist

56
Q

3 repulsion/attraction

A

Like magnetic poles repel

Unlike magnetic poles attract

57
Q

4 inverse square law

A

Closer you get the stronger the magnetic force

The farther away you get the weaker the magnetic force

58
Q

5 magnetic induction

A

The magnet can induce as it gets closer and closer and the further away the magnets no longer magnetized

59
Q

Magnetic susceptibility

A

A metal that’s easily magnetized and is also easily demagnetized

60
Q

Magnetic retentivity

A

A metal that’s difficult to magnetize and is also difficult to demagnetize

61
Q

Electric charges in motion produce what

A

Magnetic fields

62
Q

mA

A

Milliamperage
Found on nearly all X-ray machines
Causes the number of electrons and the number of the photons produced to vary

Radiologic Physics (3 decks)

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