P2- conservation and dissipation of energy 🏠🧱

Question 1

What is the law of conservation, of energy?

Answer 1

• the law of conservation of energy states: energy cannot be created or destroyed; energy can be transferred usefully, stored or dissipated.

Question 2

Fill in the gaps: ______ causes energy to be transferred to thermal energy.

Answer 2

• Friction causes energy to be transferred to thermal energy.

Question 3

How can we reduce energy transfers by reducing friction

Answer 3

• We could use a lubricant [For example, oil on the fixed point- in terms of a pendulum]

Question 4

What is a problem that can be encountered when using the efficiency equation?

Answer 4

• Sometimes you might write the efficiency equation upside down.
• To know if you’ve done this, the value will be greater than 1, or greater than 100% which isn’t possible.

Question 5

Referring to a pan, how can we increase the efficiency of an energy transfer? [4]

Answer 5

• use a lid.
• and if using a pan, use a pan with a wider base.
• place the heating element inside the water.
• have plastic walls and a lid beaus plastic is a poor thermal conductor.

Question 6

What are the two factors that affect the cooling of a building ?

Answer 6

• thermal conductivity: the higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across that material.

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Question 7

Explain how thermal conductivity of a buildings can be ‘fixed’ ?

Answer 7

• Modern houses are built from two layers: external brick and internal breezelock; there’s a cavity bewteen the walls. thermal conductivity of walls built like this, have a high thermal conductivity= lots of thermal energy can transfer out of the house.
• So to correct this, builders pack the cavity which an insulating material that has a low thermal conductivity- therefore less thermal energy escapes through the wall and passes out of the house.

Question 8

Explain how thermal conductivity of a buildings can be ‘fixed’ ?

Answer 8

• thermal energy can escape through windows and single glazed windows have a high thermal conductivity, so most houses now have a double glazed window= low thermal conductivity= less thermal energy can pass through and leave the house interior.
• Because lots of thermal energy can escape through the roof of a house= loft insulation can reduce this, because it has a low thermal conductivity= reduces the way at which thermal energy passing through.

Question 9

Excluding constructing buildings, using materials with a low conductivity. Explain how else cooling from buildings can be reduced.

Answer 9

• building houses with thick walls= reduces the rate of thermal energy transfer.