physics dont know

Question 1

best emitter /absorber

Answer 1

matt black

Question 2

voltage

Answer 2

energy transfer per unit charge passed

Question 3

filament lamp graph / explanation

Answer 3

atoms in filament vibrate causing more collision with electrons slowing them down increasing resistance

Question 4

thermistor/ ldr graph or explanation

Answer 4

heat / light energy releases more free electrons to flow

Question 5

downward force

Answer 5

is weight NOT GRAVITY

Question 6

continuous data

Answer 6

measurable range of values

Question 7

discrete data

Answer 7

separate values you count

Question 8

oscilloscope method to find freq

Answer 8

• connect to microphone
• adjust time base to get a complete cycle on the screen
• measure no. squares for 1 cycle
• times by time base
• use f = 1/t

Question 9

absolute magnitude

Answer 9

-5 - brightest
0
+5 - least bright

Question 10

atmospheric pressure

Answer 10

100kPa

Question 11

necessity of control rods

Answer 11

• without there will be too many neutrons
• too many fissions
• too much energy - melts down

Question 12

energy released in fission as

Answer 12

movement of daughter nuclei

Question 13

why wind / rain could cause rollercoaster roll back

Answer 13

wind - air resistance increases
wet - sloppy - less energy transfer to car during launch

Question 14

higher refractive index

Answer 14

more bending

Question 15

virtual image

Answer 15

• can be formed on screen
• rays don’t acc come from there

an optical image formed from the apparent divergence of light rays from a point,
as opposed to an image formed from their actual divergence

Question 16

how can you tell from a diagram there is a virtual image

Answer 16

rays don’t actually meet at image

Question 17

TIR conditions

Answer 17

i>C
more dense to less dense

Question 18

why reflected waves received for longer

Answer 18

• reflected from diff depths
• pulses travel diff distances

Question 19

ac effect on field made

Answer 19

weaker magnetic field as it’s changing direction

Question 20

why newton meter is wrong

Answer 20

scale too small to show actual value

Question 21

temp reaches steady level when heated why?

Answer 21

• heat is lost to surroundings
• rate of loss = rate of supply

Question 22

why transformers have soft core

Answer 22

easily magnetised and demagnetised
magnetic field changes so has to be able to magnetised and demagnetised easier

Question 23

transformer method

Answer 23

• steps up/ down V
• current in coil1 makes magnetic field
• current is changing ac
• field changes
• core strengthens field
• field interacts with coil2
• inducing V in coil2

Question 24

why curved magnet is better for motor

Answer 24

• force is increased (stronger field)
• radial magnet acts in all directions
• coil remains in field for long time

Question 25

how to use radioactivity to date bones

Answer 25

• living things all contain carbon
• C14 is radioactive
• over time radioactivity decreases
• know half life of C14 from other sources
• can see how long since it was alive (how many half lives)

Question 26

positives of high voltage transmission

Answer 26

• lower current as VI= VI
• more efficient as less energy used so less pollution
• transmits energy further eg national grid
• uses thinner cables
• less heating by high I so less power loss

Question 27

why does pressure act in all directions

Answer 27

• particles move at random
• collide with all walls
• force per unit area is same on all sides of the cylinder

Question 28

why is a moons gravitational force less if it has a bigger mass

Answer 28

• larger radius
• lower density
• smaller core

Question 29

electric current

Answer 29

rate of flow of charge

Question 30

red vs blue light refraction

Answer 30

• longer wavelength means less bending so red is refracted less

Question 31

irridation

Answer 31

• radiation hits object
• object not radioactive
• can be shielded
• stops when source removed

Question 32

contamination

Answer 32

• source is in/ on an object
• object radioactive as long as source is in it
• can’t be blocked
• hard to remove

Question 33

R in series

Answer 33

Rt = R1 + R2
if adding a component resistance increases

Question 34

R in parallel

Answer 34

Rt = Vt/ It
if adding component total resistance decreases