Unit D - Section 3 and 4 Test

While cutting the lawn you get tired and take a break to regain some energy. What is the scientific meaning of the term energy?

• The transfer of a force

• The ability to do work

• The conversion of work

• The force needed to do work

If you wanted to measure the amount of energy released when 1 L of gasoline is used by a gasoline engine, the unit used would be the

• joule

• kilometer

• ampere

• watt

Stephanie decides to make a pot of tea. She fills the electric kettle with water, plugs it in, and waits. After a few minutes she hears the kettle whistle, which tells her the water is hot. What energy conversion takes place in an electric kettle?

• electrical to sound

• electrical to thermal to sound

• electrical to thermal

• electrical to chemical and sound

Maria and her mother decide to bake some chocolate chip cookies. Maria’s mother asks her to preheat the oven by turning it on. When Maria looks inside the oven she sees the element glowing a bright orange and when she touches the door she can feel the heat. What is happening?

• Chemical energy is being converted into light energy, some of which is then converted into thermal energy.

• Chemical energy is being converted into thermal energy, some of which is then converted into light energy.

• Electrical energy is being converted into light energy, some of which is then converted into thermal energy.

• Electrical energy is being converted into thermal energy, some of which is then converted into light energy.

Power companies provide electricity to homes in the form of alternating current (AC), yet many devices in our homes require direct current (DC). What is the difference between alternating current and direct current?

• Direct current is less expensive to produce than alternating current.

• Direct current cannot be conducted through overhead power lines

• Direct current is electricity that flows in only one direction.

• Direct current requires only a single wire to pass through.

Tracy is replacing the light bulb of a lamp in her family room. The power rating marked on the bulb is 60 W.

This means that the light bulb uses

• 60 A/s

• 60 J/s

• 60 Ω/s

• 60 V/s

In science class you learn about power ratings, which are given in watts and calculated by multiplying the current by the voltage of a system. Your teacher explains that by rearranging the formula for power ratings, you can also calculate the current or voltage of a specific device. When you get home you read that your hairdryer has a power rating of 1600 W and a voltage rating of 125 V. What is the current, in Amperes (A), passing through the hairdryer?

• 12.8 A

• 0.078 A

• 200 A

• 78.1 A

One of the greatest inefficiencies experienced in devices that convert electrical energy into mechanical energy is due to the loss of energy through friction. One way to increase efficiency by reducing the amount of energy lost to friction is to

• Apply a lubricant to moving parts

• Reduce the input energy to moving parts

• Slow down the moving parts

• Speed up the moving parts

While visiting a power-generating plant near Edmonton, you learn how fossil fuels are used to produce electrical energy. You are told that the coal is crushed into a powder before it is blown into a combustion chamber where it is burned to release heat. Why is the coal crushed prior to burning?

• To increase the reaction rate of the combustion of coal to produce heat

• Because the coal is only combustible in its powdered form

• To allow the coal to be transferred into the combustion chamber more easily

• To decrease the reaction rate of the combustion of coal to produce a constant heat source

In science class, you learned that approximately 20 % of the world’s electricity is produced by hydro-electric generators. In order to be viable, these generators must be placed across rivers with large volumes of water passing through them. How does a hydro-electric generator produce electricity?

• A hydro-electric generator produces electricity via chemical reactions involving water.

• A hydro-electric generator produces electricity via chemical reactions involving water.

• A hydro-electric generator converts the energy of flowing water into electricity.

• A hydro-electric generator converts the energy of heated water into electricity