incorrect exam questions

Question 1

why does a magnet fall more slowly in a copper tube?

Answer 1

• force on magnet
• force opposes the motion OR force on magnet due to magnetic field caused by current in tube

Question 2

why very high temp needed to force two H nuclei together?

Answer 2

• high temperature produces high energy
• the molecules repel eachother
• both are postively charged/have like charges

Question 3

What happens to the light after it passes the lens

Answer 3

• is focused
• travels toward a point
• diverges or spreads out from that point

Question 4

how energy from the sun to be warming roads

Answer 4

• radiation
• light/infrared
• travel through space
• absorbed by road

Question 5

cool wind how

Answer 5

• density decreases and air rises
• air is replaced by cool air

Question 6

evaporatop

Answer 6

• higher speed molecules escape
• adverage kinetic energy of the molecules decreases
• temeprature is related to speed

Question 7

why metals can conduct electricity

Answer 7

atoms vibrate and hit the delocalied electrons
electrons travel through the metal and hit atoms
transferring heat

Question 8

how to use a stop watch to determine the time period of the pendulum

Answer 8

• use stop watch to time oscillations
• use of fiduciary aid to detemine a complete cycle
• use of multiple oscillations and division

Question 9

How a gas exerts a pressure:

Answer 9

• moving particles hit walls
• momentum changes when particles hit walls
• force exerted by particles due to rate of change of momentum
• P = F/A

Question 10

How does thermal energy transfer to worker whos of a distance to the metal

Answer 10

• By radiation
• EM waves, like infrared, travel to the worker
• are absorbed by the worker

Question 11

why would magnet move left if north to north?

Answer 11

force is in the direction of the field

Question 12

specific latent heat of fusion

Answer 12

energy transferred when 1kg of a substance freezes or melts

Question 12

why mixture of ice and water remain at a lower temp after 10 mins than mixture of water

Answer 12

energy is needed for change of state so temperature doesn’t rise until this has taken place
mixture of ice and water will remain at 0 until all ice has melted

Question 13

Explain, in terms of molecules, how the evaporation of sweat cools the person.

Answer 13

• in evaporation more energetic molecules escape
• lower energy molecules remian so remaining liquid is cooler
• thermal energy is taken from person to liquid

Question 13

how does wind increase evaporation?

Answer 13

wind blows fast moving molecules away OR ensure molecules do not re-enter the liquid

Question 14

if wider gap, what happens to waves in diffraction?

Answer 14

waves will pass through gap, remaining straight
as less diffraction occurs

Question 15

EMF definition

Answer 15

energy supplied to drive a unit charge round a complete circuit

Question 16

safety precautions which hospital staff taken when workiing with y-ray sources

Answer 16

• store in lead lined boxes
• limit expsoure time
• stand behind wall
• don’t let pregnant staff to work

Question 17

Iodine-131 emits γ-radiation. It has a half-life of 8 hours.
Explain why this emission and this half-life make iodine-131 a suitable material for a tracer in medical diagnosis.

Answer 17

• y can be detected outside the body
• long enough half life to be detected
• short enough half life to soon have very little activity
• weakly ionising or pass out of body without harm

Question 18

kWh

Answer 18

energy transferre in one hour at the rate of transfer of 1kW

Question 19

Explain, in terms of forces and distances between particles, why the gas occupies a much greater volume than it does as a liquid.

Answer 19

Forces between particles are much greater in liquids than gases
Particles in gases are further apart

Question 20

) We can see light from the Sun but we cannot hear any sound from it. WHY

Answer 20

sound needs a medium to travel through
light doesnt need a medium to travel through

Question 21

voltage

Answer 21

work done in passing a charge through a component

Question 22

EMF formula

Answer 22

W/Q = E
work done/charge = emf

Question 23

Explain what happens in the circuit you have drawn in (c)(i) when the temperature of the thermistor is increased.

Answer 23

resistance decreases
resistance in circuit decreases
current in circuit increases

Question 24

how determine direction of force in a motor

Answer 24

• current, magnetic field, motion at right angles to eachother
• magnetic field is from north to south
• current is from positive to negative

Question 25

State and explain what happens to the coil as it reaches the vertical position.

Answer 25

• (at the vertical) the coil stops
• (at the vertical) turning effect is zero

Question 26

Effects of split ring commutator and the brushes

Answer 26

• brushes ensure the current is maintained
• coil rotates continuously
• without wires getting tangled
• every half turn

Question 27

nuclear fission

Answer 27

when a neutron hits a large and unstable nucleus, splitting the nucleus into smaller nuclei and releasing large amounts of energy

Question 28

nuclear waste (+) and (-)’s

Answer 28

(+) continuous supply of energy
(+) not affected by weather
(+) produces large amounts of energy
(-) not renewable
(-) danger if any leak of radiation
(-) produces hazardous waste

Question 29

Explain, in terms of molecules, how sweating helps to cool your body on a hot day

Answer 29

• energy in the skin is transferred to sweat
• these molecules have enough KE to escape from the skin and become water vapour
• leaving behind molecules with lower energy
• which leaves the skin at a lower temperature

Question 30

The heating element in Fig. 4.1 remains switched on. The temperature of the sand remains constant at a value above room temperature.
Explain why the temperature of the sand remains constant.

Answer 30

• Energy is constantly lost from the sand to the surroundings
• the rate of energy supplied to sand is equal to the rate of energy lost from the sand

Question 31

difference between slip and split rings

Answer 31

slip rings => generators
split rings => dc motors

Question 32

Explain how rotating the coil in Fig. 6.2 continuously causes the galvanometer needle to show an alternating current.

Answer 32

it cuts field between the magnets
inducing an emf
this produces a current in the galvanometer
direction of current flow changes with each 180 degree rotation of coil

Question 33

Explain the operation of a basic transformer.

Answer 33

An alternating current in the PC
Produces a changing mangetic field
Field induces an EMF in secondary coil

Question 34

Describe how the americium-241 ionises air.

Answer 34

Alpha particles (emitted from americium) hit molecules in the air and remove electrons

Question 35

Suggest and explain two reasons why smoke detectors use an isotope that emits α-particles rather than an isotope that emits γ-radiation.

Answer 35

• Alpha not penetrating and is stopped by smoke particles
• alpha more highly ionising and ionises the air more easily
• short range so less harmful to humans

Question 36

Explain, in terms of the particles of the metal, why the decrease in the volume of the metal is less than that of the gas.

Answer 36

• forces between particles are larger than gases
• particles are closer together OR are already touching

Question 37

Explain why the red light does not change direction as it enters the plastic block.

Answer 37

angle of incidence = 0 so angle of refraction = 0

Question 38

difference and similiarites between emf and pf

Answer 38

both relate to energy per unit charge (E = W/Q)
emf applies to the whole circuit, while pd applies to one component

Question 39

lamp get brighter why (thermistor and potential divider question)

Answer 39

the resistance of thermistor reduced
voltage increases
current in lamp increases

Question 40

why light changes direction (refraction)

Answer 40

one side of the wavefrot enters the solid first
the side slows down first
the other side continues to move at the original speed causing turning