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- 1Kelly opens the front door on a very cold morning. Her mother complains that the house is getting cold. Use you ideas about energy flow and explain why the house gets cold.Energy flows from a warm to a cooler body; temperature of the warmer body falls.
- 2Explain the difference between temperature and heat.Temperature is a measure of heat in an arbitrary scale; heat is a form of energy on an absolute scale.
- 3A police helicopter uses a thermal imaging camera to take a picture at night. It is looking for a car that has recently been abandoned in a field after a high speed chase. Describe how the thermogram can help locate the car.A thermogram uses colour to represent different temperatures; the car engine/tyres/exhaust will be hot; a thermogram will show colours representing the high temperature against the cold field.
- 4Finish the sentence. The energy needed to raise the temperature of 1kg of a material by 1oC is known asSpecific heat capacity
- 5Jamie heats 500g of seawater in a beaker from 20oC to 90oC. The specific heat capacity of seawater is 3900 J/kg oC. How much energy is needed to heat the seawater?0.5 x 3900 x 70 = 136 500 J
- 6The energy supplied is greater than this. Suggest where this additional energy has been used.To heat the beaker
- 7What physical quantity is measured in units of J/kg?Specific latent heat
- 8When iron changes from solid o liquid, energy is transferred but there is no temperature change until all of the solid has changed into liquid. Use your ideas about molecular structure to explain why there is no change in temperature at the iron's melting point.Energy is need to break bonds; holding molecules together.
- 9The diagram shows a section through a double glazed window. Michael says that it is just as effective to use a piece of glass twice the thickness. Use your ideas about energy transfer to explain why double glazing is better.Particles in a solid are far apart where as particles in a gas are far apart. The gap between the glass is filled with gas and it's more difficult to transfer energy than in a solid.
- 10Explain how insulation blocks reduce energy transfer by conduction and convection.Air in foam is a good insulator and reduces energy transfer by conduction. Air is trapped and unable to more therefore reduces energy transfer by convection.
- 11Explain how the shiny foil helps to keep a home warmer in winter and cooler in summer.Energy from the room is reflected back in winter and energy from the Sun is reflected back in summer.
- 12A brick wall is a better conductor of heat than air in the cavity between the walls. Explain why.Particles are in constant motion and transfer kinetic energy - conduction. Particles in a solid are close together so transfer energy easily where as particles in a gas are far apart so it's more difficult to transfer energy.
- 13Hot air rises. Explain why.Air expands when heated; density = mass + volume, so increase volume means less density.
- 14Dan heats the house with coal fires. He is told are 32% efficient. Explain what is meant by 32% efficient.Only 32% of energy input is useful as energy.
- 15Dan pays £9.50 for a 25kg bag of coal. How much of that money is usefully used in heating his house.Output = 0.32 x 9.5 = £3.04
- 16Suggest why coal fires are so inefficient?Energy is lost up the chimney
- 17What is meant by the amplitude of the wave?The maximum displacement of a particle from it's rest position.
- 18What is meant by the wavelength of a wave?The distance between two successive points having the same displacement and moving in the same direction.
- 19What is the frequency of a wave?Number of complete waves passing a point each second.
- 20Ultrasound travels through water at 1500 m/s. Dolphins can detect frequencies in the range 250 Hz to 125 kHz. Calculate the range of wavelength they can hear.Wavelength = speed divided by frequency
- 21Patrick is looking through his telescope at a distant star. Diffraction occurs at the edge of the telescope. He does not see a clear image of the star. Describe what he does see.Spikes or rings around the star
- 22Why is Morse code an example of a digital signal and not an analogue signal?Dots and dashes are a series of on and off signals, not continuously variable signals.
- 23Tina's science teacher shines a laser light onto a screen. It is a brighter than the white light from the laboratory lights. Use your ideas about frequency to explain the difference between laser light and white light.Refraction from both mirrors; reflected ray returns along the incident path.
- 24Sonia's doctor wants to look at the inside of her stomach. The doctor does so without using surgery. Describe how the doctor can see inside Sonia's stomach.Light down one set of optical fibres is reflected from internal organs and up a second set of fibres viewed by an eyepiece or camera.
- 25Write down four advantages of using photocells.Photocells don't use fuel or need cables. They need little maintenance and use a renewable energy source.
- 26A p-n junction is made from two pieces of silicon. Explain how the two pieces of silicon are different and what cause the difference.n-type silicon has an impurity added to produce an excess of electrons and p-type silicon has a different impurity to produce an absence of free electrons.
- 27Name two methods of increasing the output from a photocell.Increase the light intensity; increase the surface area exposed to light; decrease the distance to the light source.
- 28During the day, short wavelength radiation form the Sun passes through the glass in the large window and warms the room. Explain how the glass keeps the room warm during the night.During the night the walls and floor radiate infrared at a longer wavelength and this is reflected by the glass so it stays inside the room.
- 29A wind turbine transfers the kinetic energy of the wind into electricity. What does the amount of electricity produced depend on?The speed of wind
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- Flashcards on Untitled, created by caitiebell123 on 21/12/2014.
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