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Physics > Physics P2 > Flashcards

Physics P2 Flashcards

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1
Q

Was Ptolmeys Model of the universe Geocentric or Heliocentric?

A

Geocentric

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2
Q

Was Copernicus Model of the universe Geocentric or Heliocentric?

A

Heliocentric

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3
Q

What is a meteor?

A

Rocks from space that fall to earth

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4
Q

What is an asteroid?

A

Rocks left over from the formation of the solar system found in the asteroid belt between Jupiter and Mars. They come from an unformed planet.

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5
Q

What is a nebulae?

A

An interstellar cloud of hydrogen gas from which new stars are formed

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6
Q

What is a protostar?

A

the beginnings of a star when a gas cloud collapses due to its own gravity

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7
Q

Describe thermonuclear fusion?

A

Hydrogen atoms are squashed together under enormous heat and pressure in the middle of a star which makes helium and releases energy

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8
Q

When does a star become a red giant?

A

When the star runs out of fuel and dies it becomes redder and cooler.

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9
Q

What is a white dwarf?

A

The small dense white core of a medium sized star left after it dies

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10
Q

What is a supernova?

A

An enormous explosion that occurs when the fusion reactions in a massive star stop.

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11
Q

What is a neutron star?

A

The small dense core left after a supernova when a massive star dies

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12
Q

What is Galileo’s claim to fame?

A

He invented the telescope and first proposed that the earth orbited the sun

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13
Q

What observation did Copernicus make that lead him to believe that the earth orbited the sun?

A

He observed that mars sometimes moved backwards in the sky as the earth overtook it

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14
Q

Why does Red Shift prove that a galaxy is moving away? How is Blue Shift different?

A

Because as a galaxy moves away from the earth its waves get spread out and appear ‘redder’ than they should.

Blue Shift shows the waves getting shorter as a galaxy moves towards earth and they appear blue. It would show if the universe was moving in on itself.

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15
Q

How do we know that the Universe is still expanding?

A

Because all of the galaxies that we have studied have proven to be red shifted, and therefore that indicates the universe is still expanding.

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16
Q

How is cosmic background microwave radiation used a evidence for the big bang?

A

Because the background microwave radiation has been determined as being heat radiation caused by the universe cooling down from the big bang. The universe emits microwave radiation because it is 3 degrees above absolute zero.

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17
Q

What is centripetal force?

A

A force at right angles to the motion of a planet that makes it move in a circular orbit. The centripetal force on the earth is provided by the sun’s gravity.

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18
Q

What is a negative ion?

When does it happen?

A

An atom that has gained an electron to become negatively charged.
This happens when radiation hits an atom.

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19
Q

What is a positive ion?

When does it happen?

A

An atom that has lost an electron to become positively charged.
This happens when beta radiation hits an atom.

20
Q

What happens during ionisation?

What issues does this present?

A

Radioactive particles approach collide with atoms and knock electrons off them, thus making them either positively or negatively charged.
This can damage cells in the body and lead to cancer.

21
Q

Can you describe Gamma Radiation in 3 bullet points?

A
  • Gamma has no mass and no charge because it is a high frequency electromagnetic wave.
  • It is the most penetrating and least ionising the of radiation.
  • It is the smallest type of radiation we study and can be stopped by a few centimetres of aluminium.
22
Q

Can you describe Alpha radiation in 3 bullet points?

A
  • It is made of 2 protons and 2 neutrons and has a charge of +2.
  • It is the largest, most charged and most ionising type of radiation.
  • It is the least penetrating type of radiation and can stopped by a sheet of paper.
23
Q

Can you describe beta radiation in 3 bullet points?

A
  • It has a charge of -1.
  • It has a low mass.
  • It is less more penetrating but less ionising than alpha. It is less penetrating but more ionising than Gamma.
24
Q

As a definition, what is the half-life of radioactive materials?

A

The time that radioactive materials take to halve their radioactivity.

25
Q

What is a transformer?

A

A device used to increase the voltage and decrease the current.

26
Q

What voltage is electricity from the national grid supplied at?

A

25,000 V

27
Q

Complete the sentence:

If the power is transmitted at a low voltage then the current will be…

A

High

28
Q

Complete the sentence:

If the power is transmitted at a high voltage then the current will be…

A

Low

29
Q

What would be the implications of transmitting power at high current for the National Grid?

A

Energy will would be wasted heating up the power lines

30
Q

What is the role of a step up transformer?

A

A step up transformer increase voltage and lowers current.

31
Q

What is the role of a step down transformer?

A

A step down transformer is used to decrease voltage and increase current.

32
Q

What voltage does the National Grid step their power to as it is transmitted through power lines?

A

400,000 V

33
Q

Why must voltage be stepped down before it is used in the home?

A

Because household sockets operate at 230V to allow for safe usage.

34
Q

What are amps?

A

The unit fro electrical current?

35
Q

What does a question mean if it refers to the ‘Units of Electricity’?

A

The question is referring to the number of ‘kilowatt hours’ used.

36
Q

What is the kilowatt hour and why do we use it?

A

The kilowatt hour is equal to a 1 kilowatt appliance being used for 1 hour.
It is used to help us measure, and comprehend, very high amounts of energy usage.

37
Q

What is the value of 1 kilowatt hour?

A

3,600,000 Joules of energy.

38
Q

What is the value of 1KW?

A

1000W Each kilowatt is worth 1000 watts.

39
Q

What is the value of 0.6KW?

A

600W

40
Q

What are Watts the unit for?

A

Power.

Watts are the unit for power.

41
Q

What are Joules the unit for?

A

Energy.

Joules are the unit for energy.

42
Q

What is the equation for efficiency?

A

Efficiency = Useful Energy Out
————————- X100
Energy In

43
Q

What is the role of a turbine in a power station?

A

A turbine is blasted with steam and used to turn a generator, which makes electricity.

44
Q

Do Power Stations produce DC or AC electricity? How many times does it change direction in a second?

A

AC - Alternating Current. It changes direction 50 times in a second.

45
Q

What does a passive solar heater do? What can it be compared to?

A

It uses sunlight to heat up water.

It could be compared to a greenhouse as it works in a similar way.

46
Q

What is a photocell?

A

A solar panel which makes electricity from sunlight.

Physics (3 decks)

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