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spring 2015 > physics chapter 4 part 1 > Flashcards

physics chapter 4 part 1 Flashcards

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?

A

Has no free electrons and therefore not good conductors of electricity

24
Q

Examples of insulators

A

◾️rubber
◾️glass
◾️ceramic
◾️wood

25
Q

What’s an electric circuit?

A

Closed pathway composed of wires and circuit elements through which electricity may flow

26
Q

What must happen for electricity to flow?

A

The pathway for electricity must be closed

27
Q

What’s a closed circuit?

A

The pathway for electricity must be closed for electricity to flow

Switch is on

28
Q

What is an open circuit?

A

A circuit In which the pathway is broken, such as when a switch is turned off

29
Q

What’s a battery?

A

A device that produces electrons through a chemical reaction, stores an electric charge for the long term and provides an electronic potential

30
Q

What’s a capacitor?

A

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
Q

What’s a diode?

A

(Solid state rectifier) a “one way valve” device that allows electrons to flow in one direction only

32
Q

What are protective devices?

A

(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
Q

What’s a fuse?

A

A section of special wire usually encased in glass that quickly melts if the current flow rises excessively thus opening the circuit

34
Q

What’s a circuit breaker?

A

Acts like a fuse. If the flow current rises excessively the circuit breakers internal switch is tripped (opened) stopping the flow of electricity

35
Q

What’s a resistor?

A

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
Q

What’s a rheostat?

A

An adjustable or variable form of a resistor

37
Q

What’s a switch?

A

A device that opens a circuit (breaks the pathway)

38
Q

What’s a transformer?

A

A device that can increase or decrease voltage by a predetermined amount

39
Q

What does ground mean?

A

The process of connecting the electrical device to the earth via a conductor.

Protective measure

40
Q

Where the grounding wire is connected?

A

Earth via a conductor

41
Q

What is magnetism?

A

The ability of a material to attract iron, cobalt, or nickel

42
Q

What’s the three laws of magnetism?

A

◾️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
Q

What happens to the voltage when the strength of the magnet is increased?

A

Increases induced voltage

44
Q

What are the 2 forms of electromagnetic induction used in xray machines?

A

Mutual induction and self induction

45
Q

What’s mutual induction

A

The induction of electricity in a secondary coil by moving magnetic field

46
Q

What happens during electromagnetism when the current changes direction?

A

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
Q

Define Lenz’s law

A

That an induced current flows in a direction that opposes the action that induced it.

48
Q

What is self induction?

A

Fluctuating magnetic field cutting back and forth through single coil, inducing a constant secondary current that opposes the original

49
Q

What are electric generators?

A

Devices that convert some form of mechanical energy into electrical energy

50
Q

What’s an electric motor?

A

Device that converts electrical energy to mechanical energy through electromagnetic induction

51
Q

What are transformers?

A

Devices used to increase or decrease voltage (or current) through electromagnetic induction

52
Q

What’s the difference between a step up and step down transformer?

A

◾️step down- decreases voltage, increases current

◾️step up-increases voltage, decreases current

53
Q

Know the relationship between voltage and current

A

Inverse

54
Q

Know what, if anything, a transformer can do with a current?

A

In some instances a transformer may be used to increase or decrease current

55
Q

Know what else an auto transformer can be referred to as?

A

kVp selector

56
Q

What’s the principle an autotransformer operates under?

A

Self induction

57
Q

Describe an autotransformer (what it made of and looks like)

A

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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