Physics

Question 1

What is the efficiency equation?

Answer 1

Efficiency=useful energy out/total energy in

Question 2

What is the equation for pay back time?

Answer 2

Pay back time=cost of insulation/energy bill saving

eg; if double glazing costs £150 but you save £50 a year on your energy bill , the pay back time is 3 yrs. 150/50=3

Question 3

What is specific heat capacity?

Answer 3

the amount of energy needed to raise the temperature of 1kg substance by 1 degree Celsius. if something has a large specific heat capacity it will take longer to heat up as it needs more energy

Question 4

What is the equation for specific heat capacity?

Answer 4

Energy (J) = mass (kg) x specific heat capacity (J/Kg degrees Celsius) x temperature change

Question 5

What is the word equation for power?

Answer 5

power (W) = energy (J) / time (s)

Question 6

Whats the word equation for units of electricity used?

Answer 6

units of electricity used (kWh) = power (kW) x time (hours)

Question 7

Whats the cost equation?

Answer 7

cost = electrical energy used (kilowatt hours) x cost per kilowatt hour

Question 8

What are longitudinal waves?

Answer 8

waves which oscillate parallel to the direction of travel eg sound waves

Question 9

What are transverse waves?

Answer 9

waves which oscillate perpendicular to the direction of travel

Question 10

What is the equation for wave speed?

Answer 10

Wave speed (m/s) = frequency (Hz) x wavelength (m)

Question 11

What’s wrong with the Bohr model of the atom?

Answer 11

Not enough empty space and nucleus is too large

Should be incredibly small and dense

Question 12

What are isotopes?

Answer 12

Have the same number of protons but different number of neutrons

Question 13

What does alpha decay do?

Answer 13

In an attempt to become more stable, a very large nucleus will emit a fast moving helium nucleus (2 protons and 2 neutrons) we call this an alpha particle

Question 14

What is beta decay?

Answer 14

In an attempt to become more stable, a nucleus which contains too many neutrons will emit a fast moving electron, we call this a beta particle.
The electron isn’t allowed to exist so is kicked out of the nucleus
The nucleus loses and electron and gains a proton so it becomes an atom of a new element

Question 15

What is Gamma decay?

Answer 15

In an attempt to become more stable, a nucleus with too much energy will emit some of this energy as an electromagnetic wave.
There is no change to the nucleus when a gamma ray is emitted because only energy is lost

Question 16

Describe why alpha beta and gamma are called ionising radiation

Answer 16

Alpha Beta and gamma collide with an atom
Gives some of their energy to the atom which makes it lose an electron
The atom becomes a positive ion
After each collision the ionising radiation loses kinetic energy
Eventually it loses too much energy and is no longer ionising radiation

Question 17

What is ionising power?

Answer 17

The probability that the ionising radiation will ionise the atoms of the material it’s passing through

In other words: how likely it is that the ionising radiation will collide with the atoms

Question 18

What’s penetration power?

Answer 18

What material or thickness of the material will stop the ionising radiation

In Other words: how likely it is that the ionising radiation will not collide with atoms. How far through a material it can get and what can stop it

Question 19

What has the largest ionising power?

Answer 19

Alpha radiation

Question 20

What has the smallest ionising power?

Answer 20

Gamma radiation

Question 21

What has the largest penetration power?

Answer 21

Gamma radiation

Question 22

What has the smallest penetration power?

Answer 22

Alpha radiation

Question 23

What does half life mean?

Answer 23

The half life of a substance is the amount of time that it takes for half the unstable nuclei to decay

Question 24

Can we predict when an individual nuclei will decay?

Answer 24

No as radioactive decay is a random process

Question 25

What’s nuclear fission?

Answer 25

Is splitting the nucleus of an atom

The process is used to produce energy in nuclear power plants

Question 26

Who does the nuclear fission process begin?

Answer 26

The process starts when the nucleus of uranium 235 atom absorbs a neutron
This makes the nucleus unstable Mir splits into two parts and releases a number of neutrons
A large amount of energy is released

Question 27

What happens once fission has started?

Answer 27

The process keeps itself going
Some of the neutrons that are produced by splitting nuclei go on to be absorbed by other uranium nuclei
This process continues making it a chain reaction

Question 28

What is nuclear fusion?

Answer 28

Is when the nuclei of small atoms join together to make larger atoms
This is very hard to achieve but is possible within a star where the gravitational forces can force the nuclei together

It’s difficult as the nucleus of an atom is positively charged and any two nuclei will always repel each other

Question 29

What are control rods?

Answer 29

They absorb neutrons

Move in and out of the nuclear fuels to control the speed of nuclear reactions

Question 30

What is used in nuclear fuel?

Answer 30

Either uranium 255 of plutonium 239 as they are more likely to undergo nuclear fission