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BMAT > Bmat section 2 physics > Flashcards

Bmat section 2 physics Flashcards

1
Q

Describe how insulators like a cloth and a plastic rod can be charged by friction. and what is this process known as, why does it have this name

A

If a plastic rod and a cloth are rubbed against each other, one of the two will lose electrons to the other. If the rod loses electrons to the cloth, it will have less electrons and therefore will be positively charged, and the cloth will be negatively charged as it will have more electrons. This is called static electricity. it is static because, the electrons cannot move in the cloth/ rod as they are insulators, so we can say that the insulators “HOLD” the electrons

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2
Q

hazards of static electricity

A

it can cause a spark which can be dangerous
an example is when an aircraft is being refueled.
lightning is also a hazard of electrostatics

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3
Q

how is sparkling in static electricity prevented

A

by earthing
in the example of the refueling of an aircraft, both the aircraft and the truck are earthed and this prevents any charges from building up and leading to a spark

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4
Q

unit for charge

A

coulombs

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5
Q

conservation of charge rule

A

charge can be conserved but cannot be created nor destroyed

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6
Q

can positive charges move in solids? give a reason for your answer

A

no they can’t, because they are held in place by other atoms.

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7
Q

effect of distance on electrostatic forces between charged objects

A

As the distance between charged objects increase, the electrostatic force between the objects decrease (become weaker) and vice-versa

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8
Q

applications or uses of electrostatics

A

can be used in photocopier machines
can be used in laser printers
can be used in electrostatic spray painting

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9
Q

what happens when a live wire touches a metal casing that has been earthed

A

a large current will flow to the Earth and
blow the fuse, disconnecting the appliance from the power supply.
This protects users from electric shock. This also protects the wiring of the
circuit from overheating and causing a fire

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10
Q

types of current and their definitions

A

Direct current: in direct current, the flow of electric charge is in only one direction
Alternating current: in this type of current, the flow of electric charge periodically reverses direction

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11
Q

conductors and insulators, their definitions and examples

A

conductors are materials that permit electrons to flow freely from particle to particle. examples are metals, the human body, aqueous solutions…

inductors are materials that impede the free flow of electrons from atom to atom
and molecule to molecule. examples are plastics, paper, and dry air.

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12
Q

formula for current

A

charge/time

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13
Q

formular for resistance

A

voltage/current

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14
Q

formula for voltage(linking energy and time)

A

energy/time

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15
Q

formula for power(linking current and voltage)

A

current* voltage

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16
Q

the formula for energy transfer

A

power*time

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17
Q

the rule for current in a parallel circuit

A

the current in the branches of a parallel circuit add up to the total current leaving the cell

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18
Q

the rule for current in a series circuit

A

the current is the same all around the series circuit

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19
Q

what does the potential difference (voltage) tell us

A

the amount of energy transferred for each coulomb of charge moving through an electrical circuit

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20
Q

voltage in a series circuit

A

the voltage is the same across a series circuit, however, when they are more than one appliances, then the potential difference is shared between the appliances

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21
Q

potential difference in parallel circuits

A

for components connected in parallel, the potential difference across each component is the same as the potential difference of the cell

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22
Q

ELECTROMOTIVE FORCE equation

A

POWER/CURRENT

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23
Q

when can we say an ammeter has zero error

A

when an ammeter displays a reading while not connected to a circuit

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24
Q

Which waves transfer the most energy

A

Waves with the short wavelength and high frequency

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25
Q

Which colour between white and black is better at absorbing infrared

A

Black

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26
Q

Which colour between white and black is better at emitting infrared

A

Black

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27
Q

Which colour between white and black is better at keeping people warm in the winter

A

White

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28
Q

Homozygous

A

When an organism has two identical alleles(versions) of the same gene

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29
Q

Heterozygous

A

When an organism has different alleles(versions) of a gene

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30
Q

Charge on an electron
Charge on a proton

A

-1.610^19
+1.610^19

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31
Q

Potential difference (relating to work done and charge)

A

Work done/charge

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32
Q

What unit is emf measured in

A

Volts

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33
Q

Ntc thermistors

A

Resistors with a negative temperature coefficient, which means that the resistance decreases as temperature increases

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34
Q

LDRs

A

A resistor with resistance that depends on the might intensity of light that falls on it. It’s resistance decreases as light intensity increases

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35
Q

What happens when a voltage is applied in reverse in a diode.
When does a diode conduct forward current instantly

A

The diode conducts no current at all

When voltage is applied across the anode to the cathode

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36
Q

Electric power formula

A

Current Voltage= current^2 resistance = voltage ^2/resistance

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37
Q

Energy transfer formulae

A

Power *time

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38
Q

Voltage formula(that links energy with charge)

A

Energy / charge

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39
Q

Where does thermal energy always flow from? and when does the transfer of thermal energy happen

A

A region of higher temperature to a region of lower temperature

When two objects of different temperatures are placed together

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40
Q

What happens when two objects of different temp. Are placed together?

When is there no thermal equilibrium

A

A thermal equilibrium is obtained , where the hotter object will decrease in temperature and the colder object will increase in temperature until the temperature is the same

When there is a change of state of the objects

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41
Q

Thermal energy lost by the hot object is equal to?

A

The sum of the thermal energy gained by the colder object and the energy loss to the surroundings

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42
Q

Conduction

A

When heat is transmitted through a medium from one particle to another through vibrations about fixed positions

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43
Q

Examples of thermal conductors

A

Metals

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44
Q

Thermal insulators and examples

A

Materials that transfer thermal energy slowly

Gases, plastic , wood

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45
Q

Name four factors that affect conduction

A

Cross sectional area of the material (increase means greater rate of conduction)

Temperature difference across material(greater temperature difference means greater rate of conduction)

Thermal conductivity of material per unit thickness

Length or thickness of material( longer distance means slower rate of reaction)

46
Q

Formula for rate of conduction

A

Change in energy/ change in time=

kA (T1-T2/ l)

47
Q

In which states do convection normally occur

A

In fluids (gases and solids )

48
Q

Describe the process of convection

A

Liquid and gases expand when heated as density decreases with increasing temperature
The fluids in hot areas are less dense than those in cold areas, so they rise into the cold areas. The denser cold liquids falls into the hot areas
In this way , convection currents are set up

49
Q

Does radiation require any medium

A

No

50
Q

If an object is a good absorber , then it’s a good…

A

Emitter

51
Q

Which objects emit and absorb electromagnetic radiation

A

All objects

52
Q

Which colour objects are the worst and best absorbers

A

Shiny and white objects are the worst as they reflect all visible wavelengths , while darker objects are the best

53
Q

factors that affect the rate of absorption and emission of thermal radiation

A

Colour
Surface texture
Surface area
Temperature

54
Q

Dull, matte and rough objects are good…… and poor …..

Smooth surfaces are good ….. and poor……

A

Absorbers and emitters

Absorbers and emitters

55
Q

Which objects radiates heat energy faster , a thin flat object or a fat object

A

A thin flat object cos it has a larger surface area

56
Q

Specific heat capacity and equation, with units

A

The amount of energy required to raise the temperature of a unit mass by 1 degree Celsius or 1 Kelvin, without any change of state

C= Thermal energy / mass*change in Temperature
J kg^-1

57
Q

Waves

A

Phenomenon in which energy is transferred from one place to another through vibrations, without the transfer of particles

58
Q

Transverse waves and examples
Longitudinal waves and examples

A

Waves that travel in a direction perpendicular to the direction of vibrations
Examples are electromagnetic and water waves

Waves that travel in a direction parallel to the direction of vibrations
Examples are sound waves

59
Q

Wave equation

A

Wavespeed= frequency * wavelength

60
Q

Frequency equation

A

F= 1/t

61
Q

Period
Si unit

A

Time taken to generate one complete wave
Second

62
Q

Wavelength

A

Distance between two successive crests or two successive troughs in a wave

63
Q

Amplitude

A

Magnitude of the maximum displacement from the rest position of the wave

64
Q

Wavefronts are normally not straight lines , true or false

A

False

65
Q

When does refraction occur

A

When waves travel from one medium to another

66
Q

What happens to the frequency , wavespeed and wavelength when a wave bends towards the normal

A

Frequency stays constant
Wavespeed decreases
Wavelength decreases

67
Q

Laws of reflection

A

The incident ray , reflected ray and normal lie on the same plane at the point of incidence

Angle of incidence is equal to the angle of reflection

68
Q

Properties of images in a plane mirror

A

They are virtual
Upright
They are the same size as the object
They are laterally inverted
They are the same distance behind the mirror as the object is in front of the mirror

69
Q

Difference between a cone of light problem and large object problem

A

The lights rays start at the same point on the object and end at different points on the eye for cone of object problems while
the light rays start at two different points on the object and end at the same point on the eye for large object problems

70
Q

Which of reflection, refraction and refraction changes frequency bog a wave

A

None of them

71
Q

Why does light bend when it enters another medium

A

Because the speed of light changes when it enters another medium

72
Q

Refractive index

A

The ratio of the speed of light in vacuum to the speed of light in a medium

73
Q

Speed of light

A

3*10^8 m/s

74
Q

What happens when a light ray travels from a medium of lower refractive index to a medium of higher refractive index

A

It bends towards the normal

75
Q

Angle of deviation

A

The angle between the incident and the refractive ray

76
Q

Laws of refraction

A

The incident ray, refracted ray and the normal at the point of incidence all lie on the same plane

The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant(snells law)

77
Q

There are two formulas for refractive index , what are they

A

n= speed of light in vacuum / speed of light in medium

n= sin I/ sin r

78
Q

Do sound waves require a medium to travel through , if so why?

A

Yes they do
They are mechanical waves

79
Q

What determines the loudness of sound waves
What determines the pitch of sound waves

A

Amplitude

Frequency

80
Q

In which states do sound travel the fastest and slowest and why is this

A

Fastest in solids , slowest in gasses
Because particles are denser in solids(compressions and rarefractions are transmitted faster in denser media)

81
Q

What is the human audible frequency range

A

Between 20Hz to 20kHz

82
Q

Ultrasonic frequencies
Infrasound frequencies

A

Human audible frequency above 20kHz

Below 20Hz

83
Q

Speed at which electromagnetic waves travel in a vacuum

A

The speed of light , I.e (3*10^8m/s)

84
Q

Properties of EM waves

A

All EM waves transfer energy from one place to the other
They are transverse waves
They can travel through a vacuum

85
Q

In a parallel circuit , the overall resistance is ……. Than the resistance of the individual resistors

A

Smaller or less than

86
Q

What do decomposers use for respiration

A

Oxygen

87
Q

Proteases can break down other enzymes , explain why

A

Enzymes are made from proteins , and proteases break down proteins , so proteases can break down enzymes

88
Q

Nuclides

A

Type of atom whose nuclei have specific number of protons and neutrons, characterised by the energy state of the nucleus

89
Q

Radioactive decay

A

When the nucleus of an unstable isotope gives of radiation to become stable

90
Q

Is radioactive decay random? If so why?

A

Yes it is
Because scientists cannot determine when a particular nucleus will decay

91
Q

Activity
Si Unit

A

Rate a which a source of unstable nuclei decay

Becquerel(Bq)

92
Q

Equivalent of 1 becquerel

A

1 decay per second

93
Q

Device used to measure activity

A

Geiger-Muller tube

94
Q

Count rate

A

Number of decays recorded each second by a detector

95
Q

Types of radiation that can be given out by an unstable nucleus

A

Alpha particles
Beta particles
Gamma radiation
Neutrons (rare tho)

96
Q

Alpha particles (decay)

A

These are in the form of a helium atom
I’m alpha decay, a helium atom is ejected or released

97
Q

The two Rules for alpha decay

A

The atomic number decreases by two
The mass number decreases by 4

98
Q

How Beta particles (decay) are formed and what happens during beta decay

A

They are formed inside the nucleus when a neutron change into a proton and an electron
In beta decay, an electron is ejected from the nucleus at a very high speed

99
Q

Two Rules for beta decay

A

Atomic number increase by one
Masa number does not change

100
Q

Rule for gamma radiation

A

Both the atomic and mass number are not changed at all

101
Q

Penetrating ability

A

How easily a type of radiation can pass through materials

102
Q

In general , a greater mass results to
…… ionising power
…….penetration power

A

Greater
Lower

103
Q

Equation of motion

A

V^2-u^2= 2as

104
Q

Term given to when an object changes shape

A

Deformation

105
Q

Types of deformation and their meanings

A

Elastic deformation : reversed when the force is removed
Inelastic deformation: is not fully reversed when force is removed

106
Q

Hooke’s law

A

Force = spring constant *extension

107
Q

Limit of proportionality

A

A measure of the stiffness of a spring up to it’s limit of proportionality

108
Q

Shape of a force extension and type of deformation graph when
Stretched below limit of proportionality
Stretched above limit of proportionality

A

Linear and elastic deformation
Non linear and i elastic deformation

109
Q

What does the gradient of a force- extension graph before the limit of proportionality represent

A

The spring constant

110
Q

Energy stored in a spring

A

Elastic potential energy

111
Q

Formula of elastic potential energy

A

E= 0.5Kx^2
Or
E=0.5 Fx

112
Q

What devices are usually used to measure
weight
Mass

A

Spring balance/ compression balance
Beam balance/ electronic balance

BMAT (4 decks)

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