These are three questions and three answers.
1) Question 2. In a car engine, energy is converted in a number of ways to make the car run. Identify the correct order of the energy conversion in the engine of the car by this path:
Answer: B. electrical → chemical → thermal → mechanical
Explanation:
The ignition switch is turned, which sends a signal to start the car by fuel burning.
i) Turning the ignition shwitch is an electrical signal. So, the start is an electrical energy.
ii) Fuel burning is braking the bonds of the fuel to convert them into CO₂ and H₂O. This is chemical energy (such as what your body does with the food).
So far, electrical energy has been transformed into chemical energy.
Electrical → Chemical
iii) This gets the engine going, which produces heat.
The chemical reaction produces gases and thermal energy (heat).
Then, add thermal energy from the chemical reaction to the chain:
Electrical → Chemical → Thermal
iv) Then, the gases expand and move the pistons, motion. Motion is kinetic energy which is mechanical energy.
This completes our chain:
Electrical → Chemical → Thermal → Mechanical
And that is the option B. electrical → chemical → thermal → mechanical
3. When a TV is turned on, electrical energy from the wires inside the wall are transferred in many ways. Which shows the best list describing most of these conversions?
Answer: B. light, sound, and heat
Justification:
i) light: the image that you can see from the screen, is only possible because part of the energy is converted into electromagnetic radiation with wavelength of visible ligth.
ii) sound: the speakers of the TV produce soud which is other kind of wave, whose enerty is supplied by the electrical energy.
iii) heat: heat is not something that you want, but part of the energy as you can verify some parts of your TV will be hot after the TV has been working, because part of the energy is "wasted" as heat.
4. Chemical energy is stored in our food. What form of energy did this chemical energy start out as?
Answer: option A. light energy from the sun.
Explanation:
The very begining is the ligth energy from the sun.
Through photosynthesis, plants convert the light of the sun (along with CO₂ ) to produce glucose, which is food that can be transformed into energy.
Then, when you or an aninal eat plants the organism carry a series of chemical reactions which end converting the glucose into energy and cells.
