energy physics test

physics test on energy, might help ya

What is a system?

an object or group of objects

What happens when something changes in a system?

energy is transferred between its stores or to the surroundings

What is a closed system?

one where no energy can escape to or enter the surroundings and the total energy never changes

What is kinetic energy?

energy an object has because it is moving

What is gravitational potential energy?

energy an object has because of its height above the ground

What is elastic potential energy?

energy an elastic object has when it is stretched or compressed

What is thermal/internal energy?

energy an object has because of its temperature

What is chemical energy?

energy that can be transferred by chemical reactions involving foods, fuels, and the chemicals in batteries

What is nuclear energy?

energy stored in the nucleus of an atom

What is magnetic energy?

energy a magnetic object has when it is near a magnet or in a magnetic field

What is electrostatic energy?

energy a charged object has when near another charged object

How is energy transferred by heating?

energy is transferred from one object to another object with a lower temperature

How is energy transferred by waves / light and sound?

waves can transfer energy by radiation

How is energy transferred by electricity?

when an electric current flows it can transfer energy

How is energy transferred mechanically?

energy is transferred when a force moves or changes the shape of an object

Equation for gravitational potential energy (j)

mass (kg) x gravitational field strength (n/kg) x height (m)

Equation for kinetic energy (j)

½ x mass (kg) x (speed)² (m/s)

What is power?

How much work is done (or how much energy is transferred) per second.

What is work done?

The same thing as energy transferred

What is the unit of power?

watt

1 watt equals what?

1 joule of energy transferred per second

Equation for power (w)

energy transferred (j) / time (s)

Equation for elastic potential energy (j)

0.5 (n/m) x spring constant x extension ²

What is useful energy?

Energy that is transferred to useful stores

What is wasted/dissipated energy?

Energy that is transferred to less useful stores

Is energy ever entirely transferred usefully?

No, some energy is always wasted

What does all energy eventually end up as?

transferred to the thermal energy stores of the surroundings

What causes energy to be wasted in machines and why?

when work is done against the force of friction, energy is transferred to the thermal store of the machine and its surroundings

What is lubrication?

a way of reducing unwanted energy transfer due to friction

What is streamlining?

a way of reducing energy wasted due to air resistance or drag in water

What is thermal insulation used for?

a way of reducing energy wasted due to heat dissipated to the surroundings

What is efficiency?

a measure of how much energy is transferred usefully

Equation for effiency?

useful power output (w) / total power input (w)

How to calculate efficiency as a percentage?

Multiply the result the above decimal calculation by 100

What does thermal conductivity tell you?

how quickly energy is transmitted through a material

How to reduce the rate of heat loss from buildings?

the thickness and thermal conductivity of the walls and roof

How does thermal conductivity affect heat loss?

lower thermal conductivity = lower rate of heat loss

What is a thermal insulator?

a material which has a low thermal conductivity

What does the energy transfer per second through a material depend on?

• the materials thermal conductivity

• the temperature difference between the two sides of the material

• the thickness of the material

What do we use energy resources for mainly?

generating electricity, heating, transport

What does reliable mean with energy resources?

supply can be controlled to meet demand

Where does most of our energy come from?

fossil fuels

What is a non-renewable energy resource?

not replaced as quickly as they are used and will eventually run out

What are examples of non-renewable energy resources?

coal, oil, natural gas, nuclear fission

What are renewable energy resources?

they can be replaced at the same time they are used and will not run out

What are examples of renewable energy resources?

solar, hydroelectric, tidal, wave, wind, geothermal, biofuels

Main uses of coal?

generating electricity

Source of coal / oil / natural gas?

extracted from underground

Advantages of coal / oil / natural gas

• enough available right now

• reliable

• cheap to extract and use

Disadvantages of coal / oil / natural gas

• will eventually run out

• release carbon dioxide when burned and other polluting gases that are one of the main causes of climate change

What are the main uses of nuclear energy?

generating electricity

What is the source of nuclear energy?

mining elements such as uranium and plutonium

Advantages of nuclear energy?

• no polluting gases produced

• enough available right now

• large amounts of energy transferred from a very small mass of fuel

• reliable

Disadvantages of nuclear energy?

• produces nuclear waste which is dangerous and difficult and expensive to dispose of

• nuclear power plants are expensive

What is the main uses of solar energy?

generating electricity and heating

What is the source of solar energy?

sunlight either transfers energy to solar cells or solar heating panels

Advantages of solar energy?

• can be used in remote places

• very cheap to run

• no polluting gases produced

Disadvantages of solar energy?

• supply depends on weather

• expensive to buy and install

• cannot supply large scale demand

Main uses of hydroelectric energy?

generating electricity

Source of hydroelectric energy?

water flowing downhill turns generators

Advantages of hydroelectric energy?

• low running cost

• no fuel cost

• reliable

Disadvantage of hydroelectric energy?

• expensive to build hydroelectric dams

• could flood a large area behind the dams destroying habitats and resulting in greenhouse gases from rotting vegetation

Main uses of tidal energy?

generating electricity

Sources of tidal energy?

turbines on tidal barrages turned by water as the tide comes in and out

Advantages of tidal energy?

• predictable supply as there are always tides

• can produce large amounts of electricity, no fuel costs

• no pollutioning gases produced

Disadvantages of tidal energy?

• tidal barrages can harm marine animals and habitats

• can be dangerous for boats

• expensive

• supply varies depending on time of the month

Main uses of wave energy?

generating electricity

Main source of wave energy?

flowing generators powered by waves moving up and down

Advantages of wave energy?

• low running cost

• no fuel costs

• no polluting gases

Disadvantages of wave energy?

• floating generators can harm marine animals and habitats

• can be dangerous for boats

• expensive

• dependent on the weather

• cannot supply large scale demand

What are the main uses of wind energy?

generating electricity

What is the main source of of wind energy?

turbines turned by the wind

Advantages of wind energy?

• low running cost

• no fuel cost

• no polluting gases produced

Disadvantages of wind energy?

• supply depends on weather

• large amounts of land needed to generate enough electricity for large scale demand

• can produce noise pollution

Main uses of geothermal energy?

generating electricity, heating

Sources of geothermal energy?

radioactive substances deep within the Earth transfer heat energy to its surface

Advantages of geothermal energy?

• low running cost

• no fuel costs

• no polluting gases

Disadvantages of geothermal energy?

• expensive to set up

• only possible in a few suitable locations around the world

Main uses of biofuels?

generating electricity, transport

Sources of biofuels?

fuel produced from living or recently living organisms, for example, plants and animal waste

What are the advantages of biofuels?

• they can be carbon neutral

• reliable

Why can biofuels be carbon neutral?

the amount of carbon dioxide released when the fuel is burnt is equal to the amount of carbon dioxide absorbed when the fuel is grown

What are the disadvantages of biofuels?

• expensive

• growing them requires a lot of land and water

• can lead to deforestation as forests are cleared for growing the crops