Energy sources
What is potential energy?
Energy that is stored.
Name the three heat transfer methods
Conduction
Convection
Radiation
What materials slow down the transfer of thermal energy?
Winter solstice (21 June in SH)
What two factors affect the gravitational pull of an object.
Mass
Distance between objects
List the five types of kinetic energy
Mechanical
Thermal
Radiant
Sound
Electrical
Explain why a heater should be placed on a floor.
Heated air rises and so will warm you as it rises up past your body
Explain how wearing a long sleeve white shirt may actually keep you cooler.
White is a reflective colour and so will reflect light from the sun and thus its heat keeping you cooler.
What is an equinox?
When day and night are exactly the same length - 12 hours day 12 hours night
Explain why the Moon has a greater gravitational pull on the Earth even though it has a much smaller mass than the Sun
The Moon is closer to us.
What type of energy does a ball on the ground have?
None. It has transferred all of its energy.
Explain why your ice cream melts on a warm summers day.
The surroundings are warmer than the ice cream and so energy is transferred to the ice cream to warm it up to achieve thermal equilibrium. In the process the ice cream warms up and so melts.
Radiation from the Sun also plays a role here.
Suppose you’re camping in cold weather and need to keep a bottle of water from freezing overnight. What do you do?
Wrap it in a blanket/ any insulator to prevent the heat from escaping and freezing.
What three main factors causes the seasons?
Shape of the Earth
The tilt
Revolution around the Sun
How many tidal changes do you experience in a 24 hour period? And every how many hours do they occur?
4 tidal changes in a day - every 6 hours.
If you lift a book higher off the ground, how does its potential energy change? Explain what factors determine the potential energy of an object.
This is because potential energy (specifically gravitational potential energy) depends on the height of the object above the ground. The higher you lift the book, the greater the distance it has to fall, meaning it has more stored energy due to gravity.
Explain how a convection current forms
Particles near the heat source become heated, gain energy and move apart becoming less dense. They rise and cooler, denser particles sink to take their place and be warmed. And so the cycle continues
Calculate the energy efficiency of the following appliance:
Printer
Total: 120kJ
Used: 90kJ
75% efficiency. An efficient appliance as it uses more energy than it wastes.
Explain how the revolution of the Earth around the Sun contributes towards the seasons
The Earth is tilted and so in its revolution around the Sun, it is either tilted towards (Summer), away (Winter) or equally facing with the opposite hemisphere (Spring and Autumn)
What is the difference between spring tide and neap tide
Spring tide occurs when the Sun and Moon are aligned causing a greater gravitational pull in one direction causing high high tides and low low tides
Neap tides occur when the Sun and Moon are at right angles to each other and so pull in opposite directions causing a lower high tide and higher low tide
Describe how potential and kinetic energy change when a roller coaster car goes from the top of a hill to the bottom. What factors affect the amount of each type of energy at different points?
Potential Energy (PE): At the top of the hill, the car has a high amount of potential energy due to its height above the ground. This energy is gravitational potential energy, which depends on the car's height and mass. As the car starts descending, its height decreases, causing its potential energy to decrease as well
Kinetic Energy (KE): At the top of the hill, the car’s kinetic energy is low (or even zero if it starts from rest). As the car moves downward, it gains speed, causing its kinetic energy to increase. By the time it reaches the bottom of the hill, its kinetic energy is at its maximum, as all the potential energy has been converted to kinetic energy.
Imagine you’re sitting near a campfire. Explain how conduction, convection, and radiation each play a role in keeping you warm.
Radiation: The main source of warmth from the campfire is radiant heat. The fire emits infrared radiation, which travels through the air and directly warms your skin and clothing without needing any material to transfer through.
Convection: The hot air around the fire rises, and cooler air moves in to replace it. This creates a convection current, which circulates warmer air toward you. Sitting near the fire, you feel the benefit of this moving warm air, especially if there’s a breeze carrying the heat.
Conduction: Conduction is less significant in this case but still present if you’re sitting on or near something warm, like a rock heated by the fire. The heat from the rock transfers directly to your body through contact, helping to keep you warm.
How could you design an insulated container to minimize heat loss using your understanding of conduction, convection, and radiation? Describe the materials and features you would use, and explain how each one reduces heat loss through each method of heat transfer.
Conduction: To minimize heat loss through conduction, you would use materials with low thermal conductivity, such as foam or fiberglass. These materials have many tiny air pockets that slow down the transfer of heat from the inside of the container to the outside.
Convection: To reduce heat loss by convection, you can create a vacuum or add layers with sealed air spaces. A vacuum layer, like that in a thermos, eliminates air, which is the medium for convection currents, so heat cannot easily move in or out. Alternatively, multiple layers of air trapped between insulating materials prevent heat from moving freely and forming convection currents within the container.
Radiation: To reduce heat loss from radiation, you could add reflective materials, like aluminum foil or a reflective coating on the inner walls of the container. These materials reflect radiant heat back into the container, keeping it warmer for longer by preventing heat from radiating outward.
Explain how the intensity of light changes from summer to winter and how this affects the temperatures
In summer the Sun's light hits the Earth at a more direct angle resulting in intense light causing higher temperatures. In winter the Sun's light hits the Earth at a shallower angle resulting in less intense light causing a drop in temperatures.
Explain why tides occur about an hour later every day
As the Earth rotates the moon continues to revolve and so by the time the Earth gets back round to the same point (i.e. made a full rotation), the moon as moved due to its revolution and so the tides will be later each day.