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spring 2015 > physics chapter 4 part 1 > Flashcards

physics chapter 4 part 1 Flashcards

(58 cards)

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0
Q

Define electrodynamics

A

The study of electric charges in motion aka electricity

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1
Q

Define electrostatics

A

The study of stationary electric charges

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2
Q

Know three ways an object can be electrified

A

◾️friction
◾️contact
◾️induction

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3
Q

Define electric potential

A

The ability to do work because of separation of charges

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4
Q

Define current

A

An expression of the flow of electrons in a conductor

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5
Q

Define resistance

A

The property of an element in a circuit that resists or impedes the flow of electricity

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6
Q

What is electric potential measured in?

A

Volts

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7
Q

Define volt

A

The potential difference that will maintain a current of 1 ampere in a circuit with a resistance of 1 ohm

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8
Q

What is volt an expression of?

A

The difference in electric potential between two points

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9
Q

What is current measured in?

A

Amperes

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10
Q

Define ampere (& it’s relationship to volt definition)

A

May be defined as 1 coulomb flowing by a given point in 1 second.
◾️The amount of current flowing with an electric potential of 1 volt in a circuit with a resistance of 1 ohm.

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11
Q

What surrounds electrical current?

A

Magnetic field

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12
Q

What are the 2 types of current?

A

◾️direct current

◾️alternating current

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13
Q

What is DC?

A

Type of current that flows in only one direction

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14
Q

How do electrons flow with DC?

A

Negative terminal to positive terminal

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15
Q

What type of current supplies the X-ray tube?

A

Pulsating direct current

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16
Q

What’s AC?

A

Current that changes direction in cycles as the electric potential of the source changes

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17
Q

What is resistance measured in?

A

Ohms

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18
Q

Define ohm

A

The electrical difference equal to the resistance between two points along a conductor that produces a current of 1 ampere when a potential difference of 1 volts applied

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19
Q

Know ohms law

A

Stated that the potential difference (voltage) across the total circuit or any part of that circuit is equal to the current (ampere) multiplied by the resistance

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20
Q

What 4 things the amount of resistance in a conductor depends on?

A

◾️material
◾️length
◾️cross sectional area
◾️temperature

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21
Q

What’s a conductor?

A

Materials with an abundance of free electrons that allow a relatively free flow of electricity

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22
Q

What are some examples of a conductor?

A

◾️copper
◾️gold
◾️water

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23
Q

What’s an insulator?

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A

Has no free electrons and therefore not good conductors of electricity

24
Examples of insulators
◾️rubber ◾️glass ◾️ceramic ◾️wood
25
What's an electric circuit?
Closed pathway composed of wires and circuit elements through which electricity may flow
26
What must happen for electricity to flow?
The pathway for electricity must be closed
27
What's a closed circuit?
The pathway for electricity must be closed for electricity to flow Switch is on
28
What is an open circuit?
A circuit In which the pathway is broken, such as when a switch is turned off
29
What's a battery?
A device that produces electrons through a chemical reaction, stores an electric charge for the long term and provides an electronic potential
30
What's a capacitor?
It's like a battery in that it stores an electric charge but works very differently in that it can produce new electrons and stores the charge only temporarily
31
What's a diode?
(Solid state rectifier) a "one way valve" device that allows electrons to flow in one direction only
32
What are protective devices?
(Fuses and circuits) act as emergency device that "breaks" or open the circuit if there is a sudden surge of electricity to the circuit or device
33
What's a fuse?
A section of special wire usually encased in glass that quickly melts if the current flow rises excessively thus opening the circuit
34
What's a circuit breaker?
Acts like a fuse. If the flow current rises excessively the circuit breakers internal switch is tripped (opened) stopping the flow of electricity
35
What's a resistor?
A device designed to inhibit the flow of electrons, thereby precisely regulating the flow of electricity through that part of the circuit where it is placed
36
What's a rheostat?
An adjustable or variable form of a resistor
37
What's a switch?
A device that opens a circuit (breaks the pathway)
38
What's a transformer?
A device that can increase or decrease voltage by a predetermined amount
39
What does ground mean?
The process of connecting the electrical device to the earth via a conductor. Protective measure
40
Where the grounding wire is connected?
Earth via a conductor
41
What is magnetism?
The ability of a material to attract iron, cobalt, or nickel
42
What's the three laws of magnetism?
◾️that every magnet has a north and South Pole ◾️like poles repel each other, opposite poles attract each other ◾️the force of attraction or repulsion varies directly with the strength of the poles and inversely with the square of the distance between them
43
What happens to the voltage when the strength of the magnet is increased?
Increases induced voltage
44
What are the 2 forms of electromagnetic induction used in xray machines?
Mutual induction and self induction
45
What's mutual induction
The induction of electricity in a secondary coil by moving magnetic field
46
What happens during electromagnetism when the current changes direction?
The magnetic field also changes. Previous magnetic field dies away and a new one is created that is opposite in orientation and properly oriented to the new current flow direction.
47
Define Lenz's law
That an induced current flows in a direction that opposes the action that induced it.
48
What is self induction?
Fluctuating magnetic field cutting back and forth through single coil, inducing a constant secondary current that opposes the original
49
What are electric generators?
Devices that convert some form of mechanical energy into electrical energy
50
What's an electric motor?
Device that converts electrical energy to mechanical energy through electromagnetic induction
51
What are transformers?
Devices used to increase or decrease voltage (or current) through electromagnetic induction
52
What's the difference between a step up and step down transformer?
◾️step down- decreases voltage, increases current | ◾️step up-increases voltage, decreases current
53
Know the relationship between voltage and current
Inverse
54
Know what, if anything, a transformer can do with a current?
In some instances a transformer may be used to increase or decrease current
55
Know what else an auto transformer can be referred to as?
kVp selector
56
What's the principle an autotransformer operates under?
Self induction
57
Describe an autotransformer (what it made of and looks like)
Only one coil of wire around a central magnetic core. Outside wires are attached at different points along the coil and induced voltage varies depending on where connections are made.

spring 2015 (43 decks)

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