Transcript P1 (the tough bits!)

P1 (the tough bits!)
• Doppler effect/Red shift
• Earthquakes
•
Transverse Waves
Longitudinal Waves.
Oscillations are parallel to the
direction of the wave
Theories of the Universe
• Steady State Theory: The Universe has
no beginning or end, it is expanding and
new matter is being created as it expands.
• Big Bang Theory: The Universe started
about 14 billion years ago in a huge
explosion called the Big Bang. Since then
the universe has been expanding and
changing and may have an end depending on
its density. Now new matter is being
created.
Both State its Expanding..
What’s the evidence for this?
• Doppler effect
EM Spectrum
LO: Understand what is meant by the Doppler Effect and how it affects light
Red Shift
http://www.youtube.com/watch?v=FhfnqboacV0
Red Shift
To know the Big Bang Theory and it’s evidence
.
The observation of red shift is a key piece of evidence for the Big
Bang theory about the origin of the Universe.
This states that the Universe ‘began’ with a colossal explosion
13,700 million years ago and has been expanding ever since.
The other key piece of evidence for the
Big Bang theory is cosmic microwave
background
radiation (CMB).
CMB is radiation remaining
from the Big Bang explosion
and fills the whole of the Universe.
This radiation has cooled as the Universe has expanded and
is now slightly less than 3 degrees above absolute zero.
• Scientists believe that the Universe is
expanding.
• Describe how careful observation of
electromagnetic radiation from distant
galaxies as well as from the whole of space
gave evidence supporting the Big Bang Theory.
(6 Marks)
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•
•
•
•
•
•
A description to include some of the following facts:
observation of visible light led to discovery of red-shift.
galaxies are moving away from each other
CMBR detected in radio telescopes
space telescopes gave more detail of CMBR
Big Bang and Steady State theories were proposed
distances to galaxies could be determined • Big Bang could
explain red-shift • Steady State could explain red-shift The
description gives some of the following details:
• red-shift means lower frequency / longer wavelength • redshift was greatest for the most distant galaxies • red-shift
means universe is expanding • Big Bang / Steady State can
explain an expanding universe •
• only Big Bang could explain CMBR • CMBR is residual
radiation from the Big Bang The description gives some of
the following reasons for scientists beliefs • observation of
increasing red-shift with distance is a reason to believe in
expanding universe
Structure of the Earth
• Mantle- Properties of
a solid, but it can
flow. Radioactive
decay takes place,
this produces heat,
which causes mantle
to flow in convection
currents.
• Core- Made of iron
and nickel. Inner core
is solid but the outer
core surrounding is
liquid.
P and S Waves
Investigating the Earth
How do we find oil?
• Scientists use a small
explosive to produce
seismic waves.
• They place sensors
(seismometers) to detect
them.
• As the waves travel
through the earth they
gradually refract.
• If the waves move from
density material to
another they reflect –
e.g. if they go from solid
rock to a pocket of liquid
oil then the wave reflects
telling the scientist that
this is an area to look at.
Why are Seisometers useful?
• The can be used to work out the
epicentre of an earth quake.
• P and S-waves travel at different
speeds.
• Using the time difference between the
two waves you can calculate how far
away the earthquake was.
• You can draw circle on a map, using the
distance you calculated as its radius
(distance arc).
• Distance arcs from three or more
seismometers will all cross at one place
(the epicentre).
• This is called triangulation.
https://www.youtube.com/watch?v=TBss68o
Bmmk
Generating Electricity
Generators
To know how an electric current can
be generated in a wire.
The Transformer Equation
Primary voltage
Secondary voltage
=
No. of turns on Primary coil
No. of turns on Secondary coil
or
Vp
Vs
=
Np
Ns
Vs
Vp
=
Ns
Np
Transformers Continued...
Starter- Copy and complete the table
Primary
turns Np
Secondary
turns Ns
Primary
voltage Vp
Secondary
voltage Vs
100
20
400
10,000
10
50
240
12
5,000
33,000
11,000
3
Step up
or step
down
Vs
Vp
=
Ns
Np
Primary
turns Np
Secondary
turns Ns
Primary
voltage Vp
Secondary
voltage Vs
Step up
or step
down
100
20
15
3
down
400
10,000
10
250
up
1,000
50
240
12
down
15,000
5,000
33,000
11,000
down
Power Rating
• Different electrical devices have different power ratings
• They use different amounts of electrical energy over a
given time.
• The greater the power rating, the greater the amount of
energy that is used.
VS
15W
100W
Energy Units
energy transferre d
power 
time taken
energy transferred
=
power
×
time taken
J
=
W (J/s)
×
s
kWh
=
kW
×
h
1 kWh is called a “unit of electricity”.
Power companies charge per unit.
How much does electrical energy cost?
Electricity Problems
A PlayStation 4 uses a 250 W power
supply. How many units of electricity
does it use in 3 hours of gaming?
Number of units:
units of electricity
units of electricity
units of electricity
units of electricity
=
=
=
=
number of kilowatt hours
power (kW) x time (h)
0.25
x 3
0.75 kWh
How much does electrical energy cost?
Electricity Problems
A pair of ghd hair straighteners operates
at a power of 300 W and uses 0.15 kWh
of electricity. For how long were they
used for?
Rearrange equation for time:
time = number of units (kWh) / power (kW)
time = 0.15 / 0.3
time = 0.5 h
How much does electrical energy cost?
Cost of Electricity
The cost of electricity is the number of units of electrical energy
multiplied by the cost per unit:
Cost = Power x Time x
(in kW) (hours)
Cost of 1Kwh
Example 1
The PlayStation 4 used 0.75 kWh
of electricity, what is the cost at a
price of 16 p per unit?
Example 2
The straighteners used 0.15 kWh
of electricity, what is the cost at a
price of 12 p per unit?
Cost = 0.75 units x 16 p/unit
Cost = 12 p
Cost = 0.15 units x 12 p/unit
Cost = 1.8 p
Working out Cost.. The cost of
1kWh is 10p
Device
Power
Power in Time
Number of units
in watts kilowatt used
used
(W)
(kW)
(hours)
Kettle
2000
2
1
Energy = Power x time 2 x 10p =
Energy = 2 x 1 = 2kwh 20p
Phone
charger
1000w
1kW
5
Energy = 1 x 5 = 5
5 x 10p =
50p
Light bulb 100W
0.1kW
6
Energy = 0.1x 6 = 0.6
0.6 x 10p =
6p
TV
0.5
3
Energy = 0.5 x 3= 1.5
1.5 x 10p =
15 p
1.5kW
0.5
Energy = 1.5 x 0.5 =
0.75
0.75 x 10p
= 7.5p
500W
Hairdryer 1500
Total cost
Dull (matt) dark surfaces are better
absorbers of infrared radiation than shiny
light surfaces.
Which metal block will heat up quicker?
If you lived in a hot country, would you paint your
house a light colour or a dark colour?
Dull (matt) dark surfaces are better
emitters of infrared radiation than shiny
light surfaces.
Hot tea 62ºC
Hot tea 62ºC
Which tea cup will lose heat quicker?
If you had a food home delivery business, would you
deliver the hot food in dark coloured containers or
Aluminium foil?
Constant Temperatures
• For a system to stay at a constant
temperature it must absorb the same
amount of power as it radiates. This is
called an equilibrium.
• E.g. If a swimming pool at 270C radiates
1200W, it needs 1200W transferred to
it to stay at 270C.