paper2 dk

Question 1

how to vary current

Answer 1

change no. cells
using a variable resistor

Question 2

why is there a net transfer of energy/heat

Answer 2

temp outside > inside so energy is transfered

Question 3

method to measure how current varies with voltage

Answer 3

• record voltage
• record current
• change V using a variable resistor
• repeat and average
• plot graph of V and I

Question 4

advantage of high voltage

Answer 4

high V means low I as VI = VI
less thermal energy tranfered to surroundings
less energy lost - more efficient

Question 5

why waves arent affected by doppler effect

Answer 5

• no relative motion between the objects
• no wavelength change

Question 6

why particles from a higher pressure chamber reach a higher height

Answer 6

higher pressure leads to higher speed
so has more KE
have same decceleration
takes longer to reach 0 due to higher speed
so travels further

Question 7

why the sun appears not circular when close to horizon

Answer 7

light from diff parts of he sun refract different amounts
refraction is large when the sun is closer

Question 8

why a ray doesnt chnage direction

Answer 8

i = 0 and i = r so r = 0

Question 9

fusion

Answer 9

2 light nuclei
fuse to make a large nucleus
release heat energy
loses mass
E = mc^2

Question 10

moderator

Answer 10

slows neutrons
made of graphite

Question 11

control rods

Answer 11

absorbs neutrons
made of boron

Question 12

how a transformer works

Answer 12

steps down V
- current in coil makes magnetic field
- current alternates
- field changes dircetion
- core strengthens field
- field cuts coil inducing V

Question 13

why is transformer core made of iron

Answer 13

easily (de)magnetised
magnetic field is alternating

Question 14

explain why metal ball floats over a charged metal dome and reaches a maximum height

Answer 14

once too far the repulsive force is too weak so it stops being repelled
- weight acts down
- W> repulsion
- slows down and KE decreases
- GPE increases
- until KE is 0 at max height
- and only weight acts

Question 15

nucleus moves left in amagnetic field - how a nucleus behaves to experience this

Answer 15

must be charged particles moving at 90 to the magnetic field and moves down

Question 16

why fusion at high temp/pressure

Answer 16

• same chrge nucleus so repel
• high temp/ pressure needed to overcome repulsive force
• not enough KE

Question 17

momentum

Answer 17

remember to use + and -

Question 18

disadvantages of wind turbines

Answer 18

• noise pollution
• ruin habitat

Question 19

how attraction affects momentum

Answer 19

• momentum increases as closer due to force of attraction increasing so velocity increases

Question 20

how transformers are useful in transmission

Answer 20

step up
- increase voltage
- lower current
- less energy lost as heat
- more efficient
step down
- voltage decreased for safe use

Question 21

harmful effect of infrared vs microwaves

Answer 21

skin burns
microwaves - internal heating of body tissue

Question 22

why is there no radiation

Answer 22

similar temps so no radiation - or solids/ liquids

Question 23

why not newtons 3rd law

Answer 23

not same type of force eg weight is balanced by gravitational force
acts on a single object not diff objects

Question 24

how is an electromagnet formed

Answer 24

coil of wire
around an iron core
current in the wire
creating magnetic field

Question 25

which store decreases in nuclear fusion

Answer 25

nuclear

Question 26

why stop clock not used and data logger used instead

Answer 26

human reaction time
- too small a value wpuld be skewed too much

Question 27

principle of moments

Answer 27

sum of ACWM = sum of CWM in equilibrium

Question 28

why diff gradients in a changing state graph for diff objects

Answer 28

• diff temp change in same time
• diff specific heat capacities

Question 29

what info spectra gives about a galaxies movement

Answer 29

all are moving from centre
spectra is red shifted and blue shifted
shows expanding from single point
galaxy is spinning

Question 30

why H, He and C are found in spectra

Answer 30

He made in fusion
H makes up stars and used in fusion
C is formed from fusion in red giants

Question 31

why difference in measured frequencies of sound for diff buzzers

Answer 31

frequency decreases
due to doppler effect
wavelength increases as s= fY
decrease in freq of B is 2 x the decrease of A as B is closer to the source

Question 32

how to measure mag field strength - using hall probe

Answer 32

• idea of measuring mag field at different distances - use ruler
• idea of repeat and average
• distance is independent variable
• mag field strength is dependent variable
• current is a control variable
• reference to suitable second control variable
  e.g. coil (spacing or turns), the rest of the apparatus