Physics 2b- Electricity and the atom

Question 1

What is the UK’s main supply of voltage?

Answer 1

230V

Question 2

What type of current supply does the UK have?

Answer 2

AC supply (alternating current) which means the current is constantly changing direction.

Question 3

What is the frequency of the UK’s AC supply?

Answer 3

50 Hertz

Question 4

What type of current do batteries and cells supply?

Answer 4

Direct Current (DC) the current always keeps flowing in the same direction.

Question 5

What does an oscilloscope screen show?

Answer 5

It shows how the voltage of an AC supply changes with time. If a DC supply was plugged in the trace you get is just a straight line.

Question 6

What does the vertical height of the AC trace show?

Answer 6

it shows the input voltage at that point. By measuring the height of the trace you can find the potential difference of the AC supply.

Question 7

how do you work out the frequency of a trace on an oscilloscope?

Answer 7

Frequency= 1/time period (s)

time period= horizontal distance between two peaks* time base

Question 8

What did scientists originally think the atomic structure looked like?

Answer 8

The Plum pudding Theory-

JJ Thomson suggested the idea that atoms were spheres of positive charge with tiny negative electrons stuck in them.

Question 9

What experiment changed the way scientists thought the atomic structure looked like?

Answer 9

Rutherford and Marsden fired beams of alpha particles at thin gold foil, they expected that the positively charged alpha particles would be slightly deflected by the electrons in the plum pudding model.

Question 10

What happened during Rutherford and Marsdens experiment?

Answer 10

Most of the alpha particles went straight through, but the odd one came straight back at them.

Question 11

What conclusions did Rutherford and Marsden draw from the experiment?

Answer 11

Most of the mass of the atom was concentrated at the centre in tiny nucleus, and that the nucleus must have a large positive charge, since it repelled the positive alpha particles by large angles.
Most of the atom is just empty space.

Question 12

What are the masses and charges of the particles in an atom?

Answer 12

proton- mass- 1 charge- +1
neutron- mass- 1 charge- 0
Electron- mass- 1/2000 charge- -1

Question 13

What are the key features of a alpha particle?

Answer 13

has a mass of 4 and a atomic number of 2, positive charge, very ionising and can be easily stopped by things such as paper.

Question 14

What are the key features of a beta particle?

Answer 14

has no mass and a charge of -1 making it an electron. It is mildly ionising and can be stopped by things such as foil.

Question 15

What are the key features of gamma radiation?

Answer 15

not ionising, hard to stop, can be stopped by lead.

Question 16

What can alpha particles be used for?

Answer 16

fire alarms

Question 17

What can beta particles be used for?

Answer 17

medical imaging

Question 18

What can gamma particles be used for?

Answer 18

cancer treatment- to destroy cells it’s targeted at.

Question 19

What fuel is used in nuclear fission, usually?

Answer 19

uranium but sometimes plutonium

Question 20

What is the process of nuclear fission?

Answer 20

a neutron is fired at a nuclei of uranium or plutonium making the nucleus unstable and causing it to split.
Each time it splits, it spit out two or three neutrons and one might hit another nucleus causing it to split also and so the chain reaction keeps going.

Question 21

What are the advantages of nuclear fission?

Answer 21

produces a lot of energy
produces clean energy- no co2 is released
- nuclear fuel is cheap

Question 22

What are the disadvantage of nuclear fission?

Answer 22

when the nuclei splits it will form two new smaller nuclei that are radioactive. This waste is dangerous to store and difficult to get rid of, its also very expensive to dispose safely.

overall cost of nuclear power is high due to cost of power plant and final decommissioning

potential explosion.

Question 23

What is the process of nuclear fusion?

Answer 23

two light nuclei e.g hydrogen can join to create a large nucleus.
releases a lot of energy 
no radioactive waste
plenty of fuel for it available 
can only happen at high temperatures

Question 24

What is the life cycle of a main sequence star?

Answer 24

1/ a protostar is formed initially, from clouds of dust and gas due to the force of gravity pulling them in.
2/ gravitational energy is converted into heat energy, so temperature increases. Once temperature is high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei which give out mass amounts of heat and light. A star is born.
3/ star enters long stable period, the heat created by the fusion provides an outwards pressure to balance the force of gravity pulling everything in. Star maintains its energy output for millions of years due to the mass amount of energy it consumes. In this period, it is called a main sequence star.

Question 25

What is the life cycle of a star from when it forms a red giant?

Answer 25

4/ Hydrogen runs out, heavier elements such as iron are made by nuclear fusion of helium. The star swells into a red giant, if it’s a smaller star. It becomes red because the surface cools
5/ becomes unstable and ejects outer layer of dust and gas.
6/ leaving behind a hot dense solid core- a white dwarf which cools down to a black dwarf and eventually disappears.

Question 26

What is the life cycle of a star when it forms a red super giant?

Answer 26

4/ The hydrogen runs out and if it’s a big star forms a red supergiant.
5/ They begin to glow brightly again as the undergo more fusion and expand and contract forming heavy elements in various nuclear reactions. Eventually they explode in a supernova forming elements heavier than iron and ejecting them into the universe to form new planets and stars.
6/ the exploding supernova throws the outer layers of a dust and gas into space, leaving a very dense core called a neutron star.
If the star is big enough this will become a black hole.