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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
2 strength
Te stronger the magnet the more current
25
3 angle
The more flux lines it cuts the stronger the current
26
4 number of turns in conductor
The more coils the stronger the induced current
27
Electric potential
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
Current
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
Voltage
Joule per coulomb Amount of energy per unit of charge 10 volts = 10000 kV
30
Resistance
The opposition to the flow off current
31
Ohms law
Voltage = current * resistance V=IR Use the triangle
32
3 formulas for power
``` 1 P= IV Power = current (amps) * voltage 2 P = I squared R Power = current * current * resistance 3 P= V^2 / R ```
33
Anmeter
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
Voltmeter
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
Coulomb's law
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
Power
P= IV Power = current (amps) * voltage Measured in watts
37
Left hand thumb rule
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
Electric current
Goes from positive to negative
39
Electron flow
Goes from negative to positive
40
Direct current
All electrons move in the same direction | Provided by 2 wires connecting the equipment to a power source
41
Alternating current
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
Is it possible to change the current from DC to AC an back?
Yes
43
Electrical circuit
A pathway that permits electrons to move in a complete circle
44
Circuit breaker
An electromechanical device which interrupts the circuit when excess current is drawn over its rating Protects from too much electricity
45
Fuses
Protects from too much electricity Contains a metal tab that melts to break the circuit Not reusable
46
Self induction
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
Mutual induction
2 coils are placed in proximity and a varying current supplied to the first coil induces a similar flow in the second coil
48
Electromagnets
Temporary magnet because it only works when electricity is running through it
49
Non magnetic
Unaffected by a magnetic field | Wood glass plastic
50
Diamagnetic
Materials are weakly repelled by all magnetic fields | Bismuth lead
51
Paramagnetic
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
Ferromagnetic
Materials are strongly attracted by a magnet Can usually be permanently magnetized Strongest
53
5 magnetic laws
``` 1 dipoles 2 magnetic poles 3 repulsion/attraction 4 inverse square law 5 magnetic induction ```
54
1 dipoles
Dividing a magnet simply creates 2 smaller magnet having as north and South Pole
55
2 magnetic poles
No matter how much a magnet is divided both poles continue to exist
56
3 repulsion/attraction
Like magnetic poles repel | Unlike magnetic poles attract
57
4 inverse square law
Closer you get the stronger the magnetic force | The farther away you get the weaker the magnetic force
58
5 magnetic induction
The magnet can induce as it gets closer and closer and the further away the magnets no longer magnetized
59
Magnetic susceptibility
A metal that's easily magnetized and is also easily demagnetized
60
Magnetic retentivity
A metal that's difficult to magnetize and is also difficult to demagnetize
61
Electric charges in motion produce what
Magnetic fields
62
mA
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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