Conservation and dissipation of energy 1.2 Flashcards

1
Q

State the law of energy conservation

A

Energy cannot be created or destroyed (it can only be transferred into different forms)

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2
Q

State any changes in the total energy of a ball that is kicked, assuming that no external forces act

A

The total energy of the system remains constant due to the conservation of energy

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3
Q

What is waste energy?

A

The energy that is not used by the device for its desired purpose

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4
Q

Describe the energy changes that occur in a filament light-bulb

A
  • Electrical energy is transferred into light and heat energy
  • Light is a useful energy form, heat is waste energy
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5
Q

How can the efficiency of a system be increased?

A
  • Reducing waste output (by lubrication, thermal insulation etc)
  • Recycling waste output (recycling thermal waste energy as input energy etc)
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6
Q

State the consequence for energy transfer of a material with a high thermal conductivity

A

The rate of energy transfer through the material is higher than for a material with a lower thermal conductivity

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7
Q

Do double-glazed windows have a higher or lower thermal conductivity than single-glazed windows?

A

Lower, meaning less energy transfers through them

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8
Q

What key factors affect the rate of cooling of a building?

A
  • The thickness of the walls

- The thermal conductivity of the walls

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9
Q

State three methods of reducing heat loss in a building

A
  • Double glazing
  • Loft and wall insulation
  • Thicker walls
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10
Q

How can the efficiency of a mechanical machine with moving parts be improved?

A

Lubricate any moving parts to reduce the friction and therefore energy loss due to heating

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11
Q

How can the efficiency of a radiator be improved?

A

Installing metal foil sheets behind the radiator to reflect the heat back into the room rather than it being absorbed into the walls

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12
Q

How can the efficiency of boiling water in a pan be improved?

A

By placing a lid on the pan to reduce the heat loss from the top

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