Heat naturally flows from regions of [blank_start]higher[blank_end] temperature to regions of [blank_start]lower[blank_end] temperature. In winter, the warm air from a heater or heating system can flow through [blank_start]any cracks or gaps[blank_end] in the walls to the [blank_start]cool air outside[blank_end] or into the cooler garage.Adding [blank_start]insulation[blank_end] to ceilings and between the walls of a home reduces the [blank_start]heat flowing outside[blank_end] in winter and inside in summer. This makes heating and cooling more [blank_start]effective[blank_end] and makes a house more [blank_start]comfortable[blank_end]
A [blank_start]solar cell[blank_end] converts light energy from the Sun directly into [blank_start]electrical energy[blank_end]. This [blank_start]electrical[blank_end] energy is converted into the [blank_start]kinetic[blank_end] energy of the blades, as well as [blank_start]sound[blank_end] and [blank_start]heat[blank_end] energy produced by the solar fan.
In 10 minutes, a power saw used 6050 J of electrical
energy. It converted:
• 1210 J into kinetic energy
• 1520 J into sound energy
• 3320 J into heat energy.
Question (1) What is the useful output energy from the saw?
Question (2) What is the energy efficiency of the saw in percentage?
[blank_start]1210÷6050=0.2, 0.2x100= 20%[blank_end]