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Physics > paper 1 physics > Flashcards

paper 1 physics Flashcards

1
Q

what direction do electrons flow in

A

Opposite direction of the conventional current

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2
Q

Why do electrical charges move through metals?

A

They have some electrons that are free to move from their atoms

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3
Q

What happens when electrical current flows through a resistor?

A

Electrical energy is transformed into heat energy

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4
Q

In a series circuit

A
  • same current
  • the total potential difference is shared between the components
  • total resistance of components is sum of the resistance of each component
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5
Q

In a parallel circuit…

A

the total current through the whole circuit is the sum of the currents through the separate components

• the p.d. across each branch is the same

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6
Q

why adding resistors in series increases

the total resistance

A

lowers current

only one path for current to flow

any added resistance reduces the current flow

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7
Q

why adding resistors in parallel

decreases the total resistance

A

both resistors have the same p.d.

current increased

the total resistance decreased
force used is the same as the p.d.

adding a resistor creates another direction to go in

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8
Q

describe the current in a series circuit

A

the current is the same at all positions

as charge only has one path to flow

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9
Q

describe the current in a parallel circuit

A

current shared between different branches

when the charge reaches a junction it splits

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10
Q

what is the definition of power (2)

A

the rate energy is transferred

the rate work is done

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11
Q

two equations for power

A

energy transferred/ time

work done/ time

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12
Q

unit of power

A

watt W

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13
Q

Two motors lift the same mass through the same height. Motor A does this in half the time of motor B. Which dissipates the most power?

A

Motor A

Energy transferred is the same but the time taken is less

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14
Q

Two equations for power of a circuit

A

current (amperes)* potential difference (volts)
I*V

current(2)×resistance (ohmns)
= I(2)R

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15
Q

equation linking energy transferred, power and time

A

E= P*t

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16
Q

equation linking energy transferred charge (power) and potential difference

A 
E= Q*V
Q= charge, coulombs
V= potential difference, volts
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17
Q

what 3 things determine the power of a circuit device

A
  • potential difference across circuit
  • the current through the circuit
  • the amount of energy transferred in a given time
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18
Q

what is insulation

A

-reducing the rate of energy transfers by heating

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19
Q

ways of reducing unwanted

energy transfers

A

-reducing waste output
lubrication,thermal insulation

-recycling waste output
recycling thermal waste energy as input energy

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20
Q

three methods of reducing heat loss in buildings

A

double glazing, prevent energy transfer by conduction in windows

  • lot and wall insulation, prevents convection currents being created
  • thicker walls
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21
Q

practical investigating effectiveness of different insulators practical

A
  1. boil water in kettle, pour in a sealable container (beaker and lid)
  2. measure the mass of water in container
  3. uses thermometer to measure initial temp of water
  4. seal container for 5 mins, measure with stop watch
  5. remove lid, measure final temp of water
  6. pour away water and let container cool to room temp
  7. repeat experiment but wrap container in different material (foil, paper)
  8. seal and use same mass of water each time
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22
Q

Kinetic energy equation

A

kinetic energy = 0.5 × mass × speed 2

Ek = 1/2 * m *v2

kinetic energy, Ek , in joules, J mass, m, in kilograms, kg speed, v, in metres per second, m/s

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23
Q

energy transfers in a battery powered motor

A

battery coverts chemical energy into electrical energy

motor converts electric energy into kinetic energy

waste energy in the form of heat due to friction

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24
Q

Equation for gravitational potential energy

A

GPE=mgh

gpe= mass × gravitational field strength × height

Ep, in joules, J

mass, m, in kilograms, kg gravitational field strength, g, N/kg may be given)

height, h, in metres, m

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25
Q

energy transfers for a bungee jumper

A

when falling GPE converted to KE of the jumper

cord tightens, KE converted and stored as ElasticPE

at lowest point the jumpers initial GPE equals the EPE stored in the cord

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26
Q

explain why a bunjee jumper slows down once cord begins to stretch

A

kinetic energy decreases as converted to EPE

KE proportional to V(2) as KE decreases the velocity decreases as well

27
Q

Efficiency formula

A

useful output / total input

28
Q

ways to increase the efficiency of an intended energy transfer (mechanical machine, radiator, water pan)

A

machine- lubricate any moving parts, reduce friction, reduce energy loss by heating

radiator, metal foil sheets behind radiator reflect heat back into room not absorbed by wall

placing lid on pan to reduce heat loss from top

29
Q

What is a half-life?

A

time taken for half the nuclei in a sample to decay

30
Q

how half-life are related to the random nature of radioactive decay.

A
  • cannot be predicted (random) when any one nucleus will decay,
  • if the half-life is a constant the activity of a very large number of nuclei can be predicted during the decay
31
Q

what is the half life if 80 atoms falls to 20 over 10mins,

A

80/2 = 40

40/2 = 20

so two half lives in 10mins

So half-life is 5mins

32
Q

properties of a alpha particle

A
  • two protons and neutrons
  • same as a helium nucleus
  • 2-10 cm in air
33
Q

properties of beta radiation

A

charge of -1 proton
stopped by aluminium
several metres of air

34
Q

properties of gamma radiation

A

electromagnetic wave
stopped by lead and concrete
mass and charge remain unchanged

35
Q

moist ionizing and least ionizing radiation

A 
most = alpha
least = gamma
36
Q

what is the equation for net decline

A

final activity of half life/ initial activity of half life

*100

37
Q

what is electric current

A

flow of electrical charge

-connected to a cell in a complete circuit Amps (A)

38
Q

equation linking charge, current and time

A

Q= I*t
Q=charge, coulombs
I= current, amperes
t= time, seconds

39
Q

two factors does the current in a circuit depend on

A

potential difference

resistance

40
Q

4 components where resistance is not constant as current changes

A
  • lamps
  • diodes
  • thermistors
  • light dependent resistors,LDR
41
Q

what is different about current flow in diode

A
  • flows in one direction

- resistance very high, in the other direction preventing current flow

42
Q

investigating factors that affect resistance , practical

crocodile clip

A
  • set up circuit
  • attach crocodile clip to the wire, level at 0cm on ruler
  • attach second crocodile clip 10 cm away in increments
  • close switch, measure voltage and current each time
  • calculate resistance for each length using R=V/I
43
Q

what is internal energy

A 
the total kinetic energy and potential energy of all
the particles (atoms and molecules) that make up a system.
44
Q

state the consequence for energy transfer of a material with high thermal conductivity

A

The higher the thermal conductivity of a material the higher the rate
of energy transfer by conduction across the material.

45
Q

what is the equation for specific heat capacity

A

= mass × specific heat capacity

× temperature change

46
Q

what is specific latent heat

A

the amount of energy
required to change the state of one kilogram of the substance with
no change in temperature.

47
Q

equation for SLH

A

E = m * L

energy for a change of state = mass × specific latent heat

48
Q

what is the Specific latent heat of fusion

Specific latent heat of vaporisation

A

fusion – change of state from solid to liquid

vaporisation– change of state from liquid to
vapour

49
Q

what do flat spots show on a change of state graph

A

flat spots show enrgy transfer e.g. melting, condensing

this is not used to change temperature

50
Q

practical for investigating SHC

A
  • have a block of solid material for heater and thermometer
  • measure mass of block
  • wrap bock in an insulating layer, insert thermometer and immersion heater
  • connect joule meter to immersion heater
  • measure initial temperature and set p.d. to 10 V
  • start stop watch and power supply
  • as block heats use thermometer and measure temperature every minute

-do calculation for shc
or rearrange shc equation

E=Pt, P=VI

51
Q

what is a random error

A

random= unpredictable differences

reduced by making more measurements,a mean value

52
Q

what is a zero error

A

zero=equipment that isn’t zeroed properly

53
Q

what is a systematic error

A

systematic error= wrong by the same amount every time, measure correctly

54
Q

what is validity

A

where results are both repeatable and reproducible

answer the original question
repeat= same, same results
produce= someone else, similar results

55
Q

what is electrostatic electricity

A

when two insulators are rubbed together

electrons are passed from one to another

56
Q

what happens when an insulator gains or loses electrons (static electricity)

A

gains electrons= negatively charged

loses electrons= positively charged

57
Q

what is produced by movement of electrons

A

positive and negative electrostatic charges

positive static charge caused by electrons moving away

causing materials to lose some negative charge, then is left with equal positive charge

58
Q

what is density

A

tells you the mass for a given volume

59
Q

density equation

A

p= m/V

density in kg/m3
volume in m3
mass in kg

1g/cm3= 1000kg/m3

60
Q

describe density of solids and liquids

A

s and l high as particles packed close together a lot of mass for their volume

gas low density spread out

61
Q

why polystyrene has a low density

A

it has a very open structure
full of air spaces
small mass for its volume

62
Q

how to find the density of a regular solid object

A
  • use a balance to measure its mass

- measure the volume using a ruler cube = lwh

63
Q

how to find the density of a irregular solid , vase

A
  • use a balance to measure its mass
  • find volume by submerging it in a eureka can filled with water
  • by displacement the water will be transferred to the measuring cylinder
  • volume displaces= volume of object
  • then mass/volume
64
Q

density of a liquid

A

-measuring cylinder on balance and zero balance
-pour 10ml liquid into measuring cylinder and record mass
-another 10ml mcylinder record total volume and mass
repeat until mcylinder full
-each measurement use formula to find density
-take average of calculated densities

Physics (10 decks)

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