Question

Question 12 (1 point) Question 12 Unsaved

Answer 1

12) Conduction. In fact, in conduction the heat is transferred when molecules collide with each other.

13) This is called thermal equilibrium. When we put two objects with different temperature in contact, their molecules have different kinetic energies. The molecules of the object with higher temperature are more energetic, and therefore they start to transfer part of their energy (by collisions) to the molecules of the object with lower temperature, until they reach a condition of equilibrium (i.e. the kinetic energies of the molecules of the two objects will be the same), and this happens when the two objects have same temperature.

14) Convection. Convection takes place in fluids: the heat is transferred by the movement of masses of fluids, from warmer regions to cooler regions.

15) Figure is missing.

16) Mechanical->Electrical. In fact, by walking through the room (movement, so mechanical energy) the body of the person acquired more electrostatic charges, and when it touches the doorknob a spark (electrical energy) takes place, because the charges accumulated on the body find a way to reach the ground throught the doorknob.

17) Law of Conservation of Energy. Indeed, it says that energy can convert into different forms, but the total energy of an isolated system must be conserved.

18) Electrical. In the cathode-ray-tube televisions, for instance, the image on the screen is produced by a current of electrons hitting the screen.

19) The chemical energy in the food is converted to mechanical energy to give the body energy to move. The energy for our body is in fact produced by the chemical reaction of the molecules of the food, and then it is used by our body to move, for instance.

20) Convection. Most of the heater uses water, which is heated and then it starts its flow to distribute the heat, therefore by convection.

21) Figure is missing.

22) The temperature of the steel decreases and the temperature of the water increases. In fact, as we said in number 13), the steel will transfer part of its energy to the water until they reach thermal equilibrium, so the temperature of the steel will decrease while the temperature of the water will increase.

23) It is given off as other forms of energy. In particular, it is converted into radiant energy: the bulb emits light, which is electromagnetic radiation, so the energy is re-emitted as radiation.

24) When two objects collide. For instance, assuming there is a body moving with speed v and another body stationary (with same mass), when they collide the first body transfers its kinetic energy to the second body, putting it in motion.

25) Electrical -> thermal. In a toaster, there is a resistance through which current flows. Due to the Joule effect, the current flowing through the resistor causes an increase of temperature of the resistor itself, therefore the energy of the current (electrical) is converted into thermal energy, which is then used to heat the toast.