Energy Efficiency and Conservation

The First Law of Thermodynamics states that the total energy before a transformation of forms (a)   ​the total energy after it.

• is less than
• is more than
• equals

Answer explanation

The law of energy conservation states that energy cannot be created or destroyed. Therefore, the total energy before a transformation equals the total energy after it, making 'equals' the correct choice.

Tags

NGSS.MS-PS3-5

Efficiency is calculated by dividing Energy Out by Energy In and is expressed as a percentage.

• False

• True

Answer explanation

The statement is true. Efficiency is indeed calculated by dividing Energy Out by Energy In, and it is expressed as a percentage, reflecting how effectively energy is converted.

Heat energy is also called ______ energy.

• chemical

• electrical

• mechanical

• thermal

Answer explanation

Heat energy is commonly referred to as thermal energy. It is the energy that comes from the temperature of matter, distinguishing it from chemical, electrical, and mechanical energy.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-3

NGSS.MS-PS3-4

What is the process of energy transforming from one form into another form of energy?

• energy efficiency

• energy conservation

• energy transformation

• energy adaptation

Answer explanation

Energy transformation is the process where energy changes from one form to another, such as from kinetic to potential energy. This term specifically describes the conversion of energy types, making it the correct choice.

In energy transformations, "free energy" that is not available to do work usually takes what form?

• heat energy

• chemical energy

• radiant energy

• sound energy

Answer explanation

In energy transformations, free energy that cannot do work typically manifests as heat energy. This is because heat is often a byproduct of energy conversion processes, making it unavailable for useful work.

The energy efficiency of incandescent light bulbs is:

• 5%

• 10%

• 15%

• 20%

Answer explanation

Incandescent light bulbs convert about 10% of electrical energy into light, while the rest is lost as heat. Therefore, the energy efficiency of incandescent light bulbs is correctly stated as 10%.

How much energy is typically lost along electricity transmission lines?

• 30%

• 20%

• 10%

• 0%

Answer explanation

Typically, about 10% of energy is lost during electricity transmission due to resistance in the wires. This makes 10% the correct answer, as losses can vary but are generally around this figure.

What happens when a person or company sets a goal to conserve energy in a building or vehicle?

• There is a reduction of only the energy output.

• There is a reduction of both the energy input and output.

• There is a reduction of only the energy input.

Answer explanation

When a person or company sets a goal to conserve energy, they typically implement measures that reduce both energy input (the energy consumed) and energy output (the energy wasted), leading to overall efficiency.

A car transforms 100 J of chemical energy into 50 J of kinetic energy. The efficiency of this car is

• 100%

• 50%

• 20%

• 5%

Answer explanation

Efficiency is calculated as (useful energy output / total energy input) x 100%. Here, (50 J / 100 J) x 100% = 50%. Thus, the car's efficiency is 50%.

Tags

NGSS.MS-PS3-4

An ad campaign asks people to turn off lights when not in use. Is this an example of conserving energy or improving energy efficiency?

• Conserving Energy

• Energy Efficiency

Answer explanation

Turning off lights when not in use is an example of conserving energy, as it reduces overall energy consumption. Energy efficiency refers to using less energy to perform the same task, which is not the focus of this campaign.

Tags

NGSS.MS-ESS3-4