P1: Energy

Question 1

What are the types of energy store?

Answer 1

-Thermal -Kinetic -Gravitational -Elastic potential -Chemical -Magnetic -Electrostatic -Nuclear

Question 2

What are the types of energy transfer?

Answer 2

-Mechanically (by a force doing work) -Electrically (work done by moving charges) -By heating -By radiation (through the EM spectrum, e.g. light or UV radiation) Overall, energy can be transferred by heating or by doing work.

Question 3

What is the equation for kinetic energy?

Answer 3

Kinetic energy (J) = ½ x mass (kg) x velocity2 (m/s) Ek = ½ mv2

Question 4

What is the equation for gravitational potential energy?

Answer 4

Gravitational potential energy (J) = mass (kg) x gravitational field strength (N/kg) x height (m) Ep = mgh

Question 5

What is the law of conservation of energy?

Answer 5

Energy can be transferred usefully, stored or dissipated, but can never be created or destroyed.

Question 6

What is power and what is it measured in?

Answer 6

Power is the rate of energy transfer / work done, measured in watts (W).

Question 7

What are the two equations for power?

Answer 7

1) Power (W) = energy transferred (J) ÷ time (s) P = E/t 2) Power = work done (J) ÷ time (s) P = W/t

Question 8

What causes energy to be wasted?

Answer 8

Resistance and friction

Question 9

In what two ways can heating occur?

Answer 9

1) Conduction (solids) 2) Convection (liquid & gases)

Question 10

What is specific heat capacity?

Answer 10

The amount of energy required to raise the temperature of 1 kg of a substance by 1ºC.

Question 11

The formula for specific heat capacity is given (ΔE = mcΔθ). What is its symbol and unit?

Answer 11

Symbol: c

Unit: J / kg°C

Question 12

Describe how you would find the specific heat capacity of a solid block of a material.

Answer 12

• You’ll need a solid block of the material, with 2 holes for the heater and thermometer to go into.
• Measure the block’s mass using a balance.
• Wrap it in an insulating layer (decreases energy dissipated from block to surroundings).
• Connect a heater to a power supply and ammeter, and place it into one of the object’s holes.
• Place a thermometer into the other and measure the initial temperature of the block.
• Set the power supply at 10V, then turn it on and immediately start a stopwatch.
• The current transfers energy to the heater’s thermal energy store, which is then transferred to the object’s.
• The ammeter reading should remain constant.
• Measure the temperature on the thermometer every 30 seconds. Turn off the power when you have 10 readings.
• Find the energy transferred to the heater at each reading using the formula E = VIt (bc E = Pt and P = VI).
• Assuming all the energy transferred to the heater was transferred to the block, find the SHC using the rearrangement c = ΔE/mΔθ.
• The plotted relationship between energy transferred and temperature would be directly proportional.

Question 13

Describe how you could investigate the effectiveness of different insulators.

Answer 13

• Boil water in a kettle and use a balance to pour a set mass into a beaker.
• Use a thermometer to measure the initial temperature.
• Seal the beaker with a lid and use a stopwatch to leave it for 5 minutes.
• Remove the lid and measure the water’s final temperature.
• Pour away the water; allow the beaker to cool to room temperature.
• Repeat steps 1-4 (use same mass of water each time!), wrapping the beaker in a different material (foil, newspaper, bubble wrap) each time.
• The most effective insulator is that which reduces the temperature difference by the largest degree.

^{<em>This investigation could be modified to instead test how the thickness of an insulator affects heat loss.</em>}

Question 14

What are non-renewable energy resources?

Answer 14

Non-renewable energy resources are ones that cannot be replenished as they are used up. They usually do damage to the environment.

Question 15

Specifically what are non-renewable energy resources?

Answer 15

Nuclear

Fossil fuels

Question 16

Non-renewables provide most of our energy. Why?

Answer 16

They are reliable. There is enough fuel to meet current demand, and they are extracted at a fast enough rate that power plants always have fuel in stock, so they can respond quickly to changes in demand.

Question 17

What are the pros of fossil fuels?

Answer 17

• Reliable.
• Enough to meet current demand and respond to changes in demand.
• Cost effective: while the setup costs of power plants are high, running and fuel extraction costs are fairly low.

Question 18

What are the cons of fossil fuels? Give at least three.

Answer 18

• Finite/non-renewable.
• They release CO₂ into the atmosphere when burned, adding to the greenhouse effect and global warming.
• Power plants ruin the view.
• Burning coal and oil releases sulfur dioxide, causing acid rain. Reduced by taking sulfur out before combustion.
• Coal mining, especially open cast, ruins the landscape.
• Oil spillages cause serious environmental problems.

Question 19

What are the pros of nuclear power?

Answer 19

• Reliable.
• Enough to meet current demand.
• Power plants can respond to changes in demand.

Question 20

What are the cons of nuclear power? Give at least three.

Answer 20

• Finite/non-renewable
• Power plants ruin the view.
• Nuclear waste is dangerous and hard to dispose of.
• Fuel is relatively cheap, but overall cost of nuclear power is high due to cost of power plants and final decommissioning.
• Nuclear power carries the risk of a major catastrophe.

Question 21

What are renewable energy resources?

Answer 21

Natural energy sources that will never run out if we replenish them as they’re used. Most of them do damage to the environment, but less than non-renewables do.

Question 22

Why don’t renewables provide the majority of our energy?

Answer 22

• They aren’t very efficient.
• They are unreliable; they depend on the weather.
• They often can’t respond to changes in demand.

Question 23

Where and how is geothermal energy sourced?

Answer 23

Geothermal power is harnessed from underground stores of thermal energy. The source of much of the energy is the decay of radioactive elements (e.g. uranium) deep inside the Earth.

Question 24

What are biofuels?

Answer 24

Fuels taken from [recently] living materials, e.g. plant products and animal waste. -They can be solid, liquid or gas. -They can be burnt to produce electricity, or run cars, in the same way as fossil fuels.