physics chapter 4 part 1 Flashcards Preview

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Flashcards in physics chapter 4 part 1 Deck (58):
0

Define electrostatics

The study of stationary electric charges

1

Define electrodynamics

The study of electric charges in motion aka electricity

2

Know three ways an object can be electrified

◾️friction
◾️contact
◾️induction

3

Define electric potential

The ability to do work because of separation of charges

4

Define current

An expression of the flow of electrons in a conductor

5

Define resistance

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

6

What is electric potential measured in?

Volts

7

Define volt

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

8

What is volt an expression of?

The difference in electric potential between two points

9

What is current measured in?

Amperes

10

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

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.

11

What surrounds electrical current?

Magnetic field

12

What are the 2 types of current?

◾️direct current
◾️alternating current

13

What is DC?

Type of current that flows in only one direction

14

How do electrons flow with DC?

Negative terminal to positive terminal

15

What type of current supplies the X-ray tube?

Pulsating direct current

16

What's AC?

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

17

What is resistance measured in?

Ohms

18

Define ohm

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

19

Know ohms law

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

20

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

◾️material
◾️length
◾️cross sectional area
◾️temperature

21

What's a conductor?

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

22

What are some examples of a conductor?

◾️copper
◾️gold
◾️water

23

What's an insulator?

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.