Questions

Question 1

What does lubrication do to surfaces

Answer 1

It reduces the surface friction between objects this slows down wear also

Question 2

What is a system

Answer 2

An object or group of objects

Question 3

Types of lubricant ion

Answer 3

Lubricant
Oil in a motor reduces friction so less energy is lost as thermal energy

Question 4

Properties of thermal conductivity

Answer 4

Higher the thermal conductivity of material means heat travels through object more easily so higher rate of energy tranfer by conduction through material

Thermal conductivity in building
Rate of cooling is low if walls are thick
If walls are thing metal sheets hear would be lost very quickly

Question 5

What are the trends of the energy use

Answer 5

During Industrial Revolution fossil fules became important as they were easy to mine and provided lots of energy

Question 6

How does resistance change
With current

Answer 6

With current
As current increases charge has more energy
It makes it more difficult for electrons to follow through the resistor so resistant mice increases and current decreases

Question 7

How does the resistance change with temp

Answer 7

Thermistor
 In hotter temperatures the resistance is lower
 These are often used in temperature detectors/thermostats

Question 8

How does resistance change with length

Answer 8

The greater the length, the more resistance and the lower the current
o Electrons have to make their way through more resistor atoms,so itis harder than
using a shorter wire

Question 9

How does resistance change with light

Answer 9

LDR(LightDependentResistor)
 The greater the intensity of light, the lower the resistance
 So the resistance is greatest when it is dark
 These are used in automatic night lights.

Question 10

How does resistance change with voltage

Answer 10

Diodes
 Diode allows current to flow freely in one direction
 In the opposite direction, it has a very high resistance so no current can flow

Question 11

Properties of series circuit

Answer 11

• Series Circuits
  o Closedcircuit
  o Current only follows a single path
  o TotalResistance= all resistors added up
  o The current is the same everywhere

Question 12

Properties of parralel circuit

Answer 12

Parallel Circuits
o Branchedcircuit
o Currentsplitsintomultiplepaths
o Total current Into a junction=total current in each of the branches
o The potential difference is the same across each“branch”

Question 13

Why is the resisters in parralel less than then the lowest resisters

Answer 13

Two resistors in parallel will have a smaller overall resistance than just one
Because charge has more than one branch to take, so only some charge will flow along each branch

Question 14

What is ac and dc

Answer 14

AC is alternating current, which comes from the mains
Currentcontinuouslyvaries,from positive to negative (charge changes direction)

• DC, direct current, is the movement of charge in one direction only o Cells and batteries supply direct current

Question 15

What are the 3 wires

Answer 15

Live-wire-230 volts
Carries the alternating potenitiql differnce from the source

Neutral blue at 0V
Completes the circuit

Earth wire
Green and yellow wires only carries a current if they’re a fault
Safety wire to stop the appliance from becoming alive

Question 16

Properties of the transformers

Answer 16

Step-upTransformers
 Increase the pd from the power station to the National Grid
 So as the power is constant current decreases so less energy is
lost.
Step-upTransformers
 Increase the pd from the power station to the National Grid
 So as the power is constant current decreases so less energy is
lost.

Question 17

How does spacing between atoms depend density

Answer 17

• Gases have a far lower density
  o The spacing between atoms increase x10, as the particles
  have lots of energy to move,

Solids and liquids have similar densities as the space between particles does not change significantly

Question 18

Properties of em radiation from atoms

Answer 18

When electrons change orbit (move closer or further from the nucleus)
o
When electrons move to a higher orbit(further from the nucleus)
 The atom has absorbed EM radiation
o When the electrons falls to a lower orbit(closer to the nucleus)
 The atoms has emitted EM radiation
- If an electron gains enough energy, it can leave the atom to form a positive ion

Question 19

Forms of decay

Answer 19

Alphaα(aheliumnucleus)  Highly ionising
 Weakly penetrating (~5cm of air)

o BetaMinusβ(electron)  Medium ionising
 Medium penetration (few meters of air, sheet of aluminium )

o Gammaγ(radiation)  Low ionising
 Highly penetration (several meters of concrete and few cm of lead )

Question 20

Properties of half life’s

Answer 20

The half-life of an isotope is the time taken for half the nuclei in a sample to decay or the time taken for the activity or count rate of a sample to decay by half.

It cannot be predicted when any one nucleus will decay

Question 21

How is alpha radiation used in smoke detectors

Answer 21

It is an alpha emitter, and used in smoke alarms
 It is emitted into the air around the alarm, and does not reach far because alpha is weakly penetrating
 If smoke reaches the alarm, the amount of alpha particles in the surrounding air drops
This causes the alarm to sound

Question 22

What is contamination

Answer 22

Lastsforalongperiodoftime
o Thesourceoftheradiationistransferredtoanobject
 Radioactive contamination is the unwanted presence of radioactive atoms on other materials – the hazard is the decaying of the contaminated atoms releasing radiation
o E.g.radioactivedustsettlingonyourskin

Question 23

What is iridaition

Answer 23

• Irradiation
  o Lasts only for a short period of time
  oThe source emits radiation,which reaches the object
   Exposing an object to nuclear radiation, but does not make it radioactive E.g.radio active dust emitting beta radiation,which“irradiates”yourskin
  o Medical Items are irradiated sometimes to kill bacteria on its surface,but not to
  make the medical tools themselves radioactive

Question 24

What is boyles law

Answer 24

Boyle’s law is a gas law, stating that the pressure and volume of a gas have an inverse relationship. If volume increases, then pressure decreases and vice versa, when the temperature is held constant

Question 25

How does the electron agrangemtn change when an atom emits and absorbs EM radition

Answer 25

Absorbs
Electrons move further away from nucleus ,they move to a higher energy level
Emit
Electrons move closer to nucleas
They move to a lower energy level

Question 26

Why do unstable atoms give out radiation

Answer 26

Undergo decay to become more stable
As they release radiation their stability increases

Question 27

What is the unit for radioactive decay

Answer 27

Bq

Question 28

What is the count rate

Answer 28

The number of radioactive decays per second for a radioactive source

Question 29

What can be used to measure count rate

Answer 29

Geiger miller tube

Question 30

Describe the nature of radioactive decay

Answer 30

Random
Determined by chance
Impossible to predict

Question 31

What is peer review and why is inportant

Answer 31

To allow the findings to be indolently checked

Question 32

Why is the internal energy of a substance

Answer 32

The energy stored by particles
Sum of total kinetic and potential energies they make up a system

Question 33

What 3 factors determine the temp change of a system

Answer 33

Mass of substance
Specific heat capacity
Energy inputted into system

Question 34

What is specific latent heat

Answer 34

The amount of energy needed to change the state of 1kg of a substance with no change in temp

Question 35

Why does pressure increase as temp increases

Answer 35

Kinetic energy of molecules increase
More frequent collisions
Greater rate of change of momentum
Greater force and therefore pressure

Question 36

Describe the energy changes in a battery powered motor

Answer 36

Battery converts chemical energy to electrical
The motor conveys electrical energy into kinetic energy as well as a waste thermal energy

Question 37

What is the advantage of connecting lamps in parralel

Answer 37

If one lamp blows the rest of the circuit will be unaffected
And can still recive current

Question 38

How should ammeters and volt meters be placed in circuit

Answer 38

Ammeter should conncectes in a servers with the conponetntheure measuring
Voltmeter should be placed in sparkle with the commoner your testing

Question 39

What is the conspire of a transformer and how does it increase pd and decrease it and how can you tell what transformer it is

Answer 39

A transformer is formed from two coils of wire around a magnetic core. The number of coils determines whether the transformers will step-up or step-down the voltage.