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Flashcards in Physics Deck (93):
1

What does a substance that loses electrons become

Positively charged

2

What happens if charges in an ion:
Are the same.
Opposite.
One is charged the other isn't.

Repel
Attract
Attract

3

How can you tell if an insulator is charged

Two

It attracts small pieces of dust and paper

When a balloon is charged it sticks to a wall

4

Two problems with static

Dust and dirt are attracted to insulators such as computer screens

Clothes made from synthetic materials cling to each other and to the body

5

Two dangers of static

If there are flammable gases or a high concentration of oxigen a spark could ignite the gases and cause an explosion

If you touch something with an electric charge on it it gives you a shock and could cause a heart attack

6

Safety measures from static shocks

An object that might be charged is connected to the earth by a wire so any charge disapaits

In a factory workers stand on an insulator matt so charges can't be earthed through them

Lorries containing flammable liquids and gases are connected to the earth through earth through earth wire befor being loaded

When an aircraft is fueled static can build up this can causes sparks which can ignite the fuel a wire is used to earth the aircraft before it is fueled

7

What are five examples of uses of static

Photocopiers and laser printers

Defibrillators

Electrostatic dust precipitators

Paint spraying powder coats

Insecticide sprays

8

What is an electrical currant

A flow of electrical charge

9

How does a conventional current flow

From the post stove side of the terminal to the negative side

10

In what direction do electrons move compared to the conventional current

The opposite way

11

How do electrical conductress differ to insulators

Their electrons can move from atom to atom

12

What is the unit of charge

The coulomb c

13

What is the uk mains supply's voltage and frequency

230v

50hz

14

What happens to the current when the components are connected in series

The current is the same

15

What happens to the current of components connected in parallel

It is shared

16

What is the word used to describe the fact that the total current going into the split in a parallel circuit is the same as the one going out

The current is CONSERVED

17

What is the unit for current

Amperes

18

How must an ammeter be connected into a circuit

In series

19

What does a substance that gains electrons become

Positively charged

20

How must a voltmeter be connected to a circuit

In parallel

21

If two 1.5v cells are connected in series in opposite direction what is the voltage

0

22

If two 1.5v batteries are connected in series facing the same direction what is the voltage

3v

23

What is the relationship between energy transferred, potential difference and charge

Joules=voltage x coulombs (charge)

24

What is the unit for resistance

Ohms

25

What do resisters do in a circuit

Reduce the amount of current flowing

26

What is the name for a variable resistor

Rheostat

27

What happens to the current as you increase the potential difference

It increases

28

What is the equation for the relationship between resistance voltage and current

Resistance=voltage/current

R= v/a

29

What is the relationship between voltage current and resistance

Voltage=current x resistance

30

What is ohms law

The result that the current flowing through a resistor=the voltage across the resistor. Providing the temp stay the same

31

What does it mean if the current flowing through a resistor is directly proportional to the voltage across it

It follows ohms law

32

Does a filament lamp follow ohms law

No, the resistance increases as the current increases

33

What is the current potential difference graph for a diode

A straight line then a steep line going to the right

This is because diodes have a very high resistance one way so it can only flow the other way

34

What is a thermistor

Thermistors are temperature sensors their resistance decreases as the temperature increases

A use is in fire alarms

35

What is the symbol for a thermistor

A rectangle in the circuit with a line underneath it which then turns and goes through the box at a 45 degree angle

36

What are ldr's

Light dependant resistors. Used in automatic security lights. Their resistance decreases as the light intensity increases

37

What is the symbol for an ldr (light dependant resistor)

A rectangle in the circuit with a circle around it. Stows point to it in accordance to where the light is coming from

38

What is the energy transfer I'm a resistor
Plus two uses

Some of the energy from the electrical current gets turned into heat

Heating water in an electric kettle
Electric fires

39

What causes the heat transfer in wires

The free flowing electrons colliding with ions in the lattice structure of the metal each collision causes heat to transfer to the lattice

40

What happens to a resistor as it's temperature increases.

It's resistance increases

41

What is diplacement

Distance traveled in a straight line

42

What is the velocity

The velocity of an object is its speed in one pert inculcate direction

43

What are the four vector quantities of a moving object

Displacement
Velocity
Acceleration
Force

44

How do you find the distance traveled on velocity time graphs

The area below the line

45

What are the two factors in the size of acceleration

The size of the resultant force
Doubling the resultant force doubles the acceleration

The mass
Doubling mass halves the acceleration

46

What is the strength of gravity on earth

Ten newtons per kilogram

47

The three stages of falling

Acceleration downwards of the object no air resistance
Resultant force is acting downwards

Object gains speed weight stays the same but air resistance increases
Resultant force is acting downwards

Weight is balanced with air resistance there is no resultant force reaches terminal velocity

48

How do seat belts prevent injury in a car crash

Stop you moving inside the car

Stretch slightly to reduce the time taken for the body to reach zero so reduces forces on it

49

How do airbags help you survive a car crash

Increase the time for the heads movement to reach zero to reduce forces on it

Act as a cushion to stop cuts

50

What two things the amount of work done depend on

The size of the force on the object

The distance the the object moves

51

What is the relationship between work done by brakes and the loss in kinetic energy

Work by brakes=loss in kinetic energy

52

What happens to the braking distance of a car if it's speed doubles

It quadruples

53

What does power measure

How quickly work is being done

54

What is the measure of power

Watts

55

What does the amount of gravitational potential energy depend on

Mass

Height above ground

56

What are the gravitational field strengths of the earth moon and Jupiter

Earth 10n

Moon1.6n

Jupiter26n

57

What are the dependant values on the size of kinetic energy in a moving object

Speed and mass

58

What is the relationship between work done by brakes and the loss in kinetic energy

They are equal

59

What is an example of conservation of energy

Newtons pendulum

60

What makes a material radioactive

The nucleus of the atom is unstable and can decay by giving off radiation in the form of alpha particles beta particles or gamma rays

61

What is used to measure radioactivity

A Geiger counter

62

What is the activity of a radioactive material measured in

Becquerels

63

What is the activity of a radioactive material

The number of nuclei that decay and give off radiation every second

64

What is an alpha particle made of

Two protons and two neutrons, same as a helium nucleus

65

What is a beta particle made of

A fast moving electron

66

What is a gamma ray made of

High energy electromagnetic radiation

67

How well does gamma ionise

Weakly

68

How well do alpha particles ionise

Very well

69

How well do beta particles ionise

Medium

70

What happens after alpha decay

A new element is formed two places lower in the periodic table

71

What happens after beta decay

The nucleus has one more proton and one less neutron

72

Steps of fission 4

Neutron fired into nucleus

Neutron hits nucleus

Nucleus splits into smaller nuclei called daughter nuclei and releases two or three more neutrons

The released neutrons hit more uranium nuclei

73

Where is the most dangerous nuclear waste stored

Glass like blocks deep in the ground

74

How else can a nuclear reactor be used

Can make other nuclei radioactive because they absorb the neutrons which makes their nuclei unstable

These are used as tracers in hospitals

75

How do control rods reduce reaction speeds and what are they made of

When hit by a neutron the daughter nuclei make two or three extra neutrons, this reaction is a chain reaction and if not controlled would easily spiral out of control
Control rods are made of boron which absorbs the neutrons, this slows down the reaction as less neutrons are hitting new nuclei

The control rods are lowered to slow the reactiOn down and raised to speed it up

76

Two steps of fusion

Two hydrogen atom collide and fuse together

The hydrogens fuse to produce a helium atom and energy

77

What is the difficulty of nuclear fusion

Both hydrogen atoms are positively charged which causes electrostatic repulsion so it has to be very hot for the nuclei to coliseum as they then move faster

Pressure and heat have to be very high and are more expensive to produce than the energy made by fusion

78

Why was cold fusion never considered to work

Many attempts to reproduce the results failed

So it did not pass the peer review

79

How do rocks emit radiation

Radon gas emited

80

How is alpha radiation used

Smoke detectors

Americium releases alpha which ironises the air in a detector smoke from fire ionises differently and causes the alarm to go off

81

What are the uses of beta two

Medical tracers certain chemicals concentrate in damaged or diseased parts of the the body radiation detectors are placed around the body to build an image of the inside

Measuring thickness of materials

The thicker the material the more radiation is absorbed and the less radiation reaches the detector
The detector then sends signals to the machine to decrease the size of the material

82

Uses of gama

Treatment of cancer

Sterilising medical equipment no heat so plastics can be sterilised

83

What does the rate of nuclear decay depend on

The type of material

The number of un decayed nuclei present the greater the rate

84

How is carbon fourteen formed

Cosmic rays hitting he atmosphere

85

How is carbon dating done

Using the half life of carbon 14 we can judge the age of something as the amount of carbon 14 on earth always stays the same

86

How is the age of rocks found

The ratio of uranium to lead

As the rock gets older there is more lead available

87

What accounts for the most background radiation

Radon gas

88

Dangers of ironising radiation on the body

Breaks molecules into fragments
The ions then react with other molecules in cells

Charged particles can react with DNA which causes mutations and cancer

89

Five precautions around radioactivity

Using tongues to pick up sources

Surveys kept in lead containers

Sources never pointed at people

Protective clothing

Exposure times limited

90

Disadv to nuclear energy

Non renewable

If accident large amounts of radiation released

Nuclear waste stays radioactive for thousands of years

91

How is low level waste disposed

Put in drums and submerged in concrete

92

How is intermediate level waste disposed

Mixed with concrete then put in stainless steel drum

93

How is high level n waste stored

Stored under water in large pools for 20 years then put in underground store where air can circulate and cool it