P1 Energy For The Home

Question 1

What is heat

Answer 1

A measurement of internal energy. It is measured on an absolute scale.

Question 2

What is heat capacity

Answer 2

The energy needed to raise the temperature by 1 degree Celsius

Question 3

What is specific latent heat

Answer 3

The energy needed to melt or boil 1kg of the material

Question 4

Why is there no change in temperature when an object is heated and it changes state

Answer 4

Energy is needed to break the bonds that hold the molecules together, not hotness

Question 5

How does double glazing reduce energy loss by conduction

Answer 5

Between the two panes of glass there is a vacuum, therefore the particles of gas are not there making it impossible to transfer energy

Question 6

How does loft insulation reduce energy loss by conduction and conviction

Answer 6

Warm air in the home rises, air n the loft is warmed by the top of the ceiling and is trapped in the loft insulation, both sides of the ceiling are the same temperature so n energy is transferred

Question 7

How does cavity wall insulation work

Answer 7

The air in the foam is a good insulator, the air cannot move by convection because it is trapped in the foam

Question 8

How do insulation blocks reduce energy transfer by radiation

Answer 8

Energy from the sun is reflected back by the shiny foil to keep the home cool in summer, energy from the home is reflected back n to keep the house warm in winter

Question 9

What is conduction

Answer 9

Due to the transfer of kinetic energy between particles

Question 10

What is convection

Answer 10

When a gas is heated it expands making it less dense so it rises

Question 11

What diagram is used to represent energy efficiency

Answer 11

Sankey diagrams

Question 12

What is the amplitude of a wave

Answer 12

It is the maximum displacement of particles from its rest position

Question 13

What is the crest of a wave

Answer 13

The highest point of the wave above its rest position

Question 14

What is the trough of a wave

Answer 14

The lowest point of the wave below its rest position

Question 15

What is the wavelength

Answer 15

The distance between 2 successive points on a wave

Question 16

What is the frequency of a wave

Answer 16

The number of complete waves passing a point in one second

Question 17

How does the electromagnetic spectrum, go

Answer 17

Radio - microwave - infrared - visible - ultraviolet - X-Ray - gamma ray

Question 18

When does refraction occur

Answer 18

The speed of the wave decreases because it enters a more dense medium and increases when it enters a less dense medium

Question 19

What is diffraction

Answer 19

The spreading out of waves as it passes through a gap

Question 20

How does diffraction change depending on the size of the gap

Answer 20

The most diffraction occurs when the gap is of a similar size to the wavelength, larger gaps show less diffraction

Question 21

What are a laser lights properties

Answer 21

It only has one frequency, is in phase and shows little divergence

Question 22

How does a laser light read the surface of a compact disc

Answer 22

The surface of the CD is pitted, the pits represent the digital signal, laser light is shone onto the CD surface and the difference in the reflection provides the information for the digital signal

Question 23

What happens if the angle of incidence is bigger than the angle of refraction

Answer 23

The light is reflected known as total internal reflection

Question 24

What are the main uses of total internal reflection

Answer 24

In optical fibres for telephone conversations and computer data. And in an endoscope where a doctor can see inside a patients body as light is passed along the optical fibres illuminating the inside of the body, the light is reflected and passes up another set of fibres to either an eyepiece or a camera

Question 25

How do microwaves cook food

Answer 25

The microwaves penetrate 1 cm into the food then the water and fat molecules vibrate more so the energy is transferred by conduction

Question 26

How do normal ovens cook food

Answer 26

Energy is absorbed by the surface of the food causing kinetic energy to increase, then the rest of the food is cooked by conduction

Question 27

How do satellites work with microwave communication

Answer 27

The signal form earth is received, amplified and retransmitted back to earth

Question 28

What is necessary in terms of where the transmitter must be for microwave communication

Answer 28

They must be in the line of sight, so there is no obstacles in the way

Question 29

What can change the signal strength of a microwave, however it doesn’t show a lot of diffraction

Answer 29

Adverse weather, large areas of water can scatter the signal and the curvature of the earth limits the line of sight

Question 30

What is the disadvantages of mobile phones

Answer 30

It can interfere with sensitive equipment such as those in hospitals and planes

Question 31

What happens when you press a button on a TV remote

Answer 31

A coded signal is sent to an LED at the front of the remote, this includes a start command, the instruction command, a device code and a stop command. The LED transmits in a series of pulses, which is decoded by the TV allowing it to do your commands

Question 32

What are the benefits of digital over analogue

Answer 32

Improved signal quality for both picture and sound, a greater choice of programmes, being able to interact with the programme, information services such as programme guides and subtitles

Question 33

What are the advantages of digital signals

Answer 33

The frequency of the carrier wave is usually higher, the combined wave is transmitted, interference from another wave can also be added and transmitted, if the wave is amplified, the interference is amplified as well therefore analogue is bad. However digital signals multiplex allowing a large number of digital signals to be transmitted at the same time

Question 34

What is temperature

Answer 34

A measure of hotness on an arbitrary scale

Question 35

Why do radio stations broadcast on a particular frequency, and why do some radio stations have the Same frequency

Answer 35

Because then there is no interference between 2 radio stations, however sometimes the radio stations are too far away to interfere with each other

Question 36

What are the adv. and the disadvantages of DAB

Answer 36

Provides greater choice of radio stations however the quality isn’t as good

Question 37

How do radio wave work

Answer 37

They behave like an optical fibre and undergo total internal reflection by reflecting off the ionosphere and water such as the oceans

Question 38

What are some possible communication problems

Answer 38

Radio waves are diffracted when they wet an obstacle, refraction in the atmosphere needs to be taken into account when sending a signal to a satellite, transmitting aerial needs to be very focussed as the satellites aerial is very small, the beam is lightly divergent, some energy is lost form the edge of the transmitting aerial due to diffraction

Question 39

What are the 2 different types of waves and what are their properties

Answer 39

P waves - refracted by the earths core, paths taken by these sows scientists the size of the earths core, travel through the e earth
S waves - not detected on the other side of the earth, won’t travel through liquid, tells scientists earths core is liquid

Question 40

How does tanning occur

Answer 40

The tan is caused by ultraviolet light on the skin, cells in the skin produce melanin causing tan.
People with darker skin do not tan as easily because the ultraviolet radiation is filtered out

Question 41

What happens penned to the ozone layer and why

Answer 41

The ozone layer is found in the stratosphere and it helps to filter out ultraviolet radiation, however it became very thin at the South Pole, this was due to CFC gases being used from aerosols and fridges. Happened because ozone depleting chemicals work best in cold temperatures