HEAT AND HEAT ENGINE

What is heat engine?

• It is a device that converts electrical energy into heat energy.

• It is a device that converts thermal energy into chemical energy.

• It is a device that converts thermal energy into mechanical energy.

• It is a device that converts chemical energy into mechanical energy.

Why does heat engine cannot be 100% efficient?

• Some of the steam cannot make the turbines to move.

• The energy converted to mechanical energy is not enough.

• It is because all heat is converted into work to perform its function.

• It is because part of the heat input is utilized for the mechanical work and

  some heat input cools down due to friction and for the cycle to happen.

Heat engine like in a geothermal power plant follows series of pattern in

its operations. How will you arrange the following in correct sequence?

I. Part of the heat is used to do mechanical work on an object.

II. Condensed water is brought back to the Earth to repeat the cycle.

III. Heat is supplied to the engine by an external source called hot reservoir.

IV. Some of the heat decreases its temperature and condenses back to

water.

• I, II, III, IV

• I, III, II, IV

• III, I, IV, II

• III, IV, I, II

If you will have a company business in the future using heat engines, why

will you intentionally run the engine at a high operating temperature?

• A heat engine reduces the heat energy from a heat source.

• Heat engine depends primarily on the temperature difference.

• The lower is the temperature of the input heat, the greater is the energy

  for power production.

• The higher is the steam temperature driving the turbine, the higher is the

  efficiency of the power production

One of your daily routines is to have a cup of hot coffee early in the

morning. You have to boil water using kettle. Why does whistling kettle

whistles?

• a. Water boils.

• The water increases its temperature.

• When the water boils, it produces steam that makes the cover to move.

• At extremely high temperature, water boils then changes its phase into

  steam that causes vibration as it passes through a tone hole of the whistling

  kettle.

Which of the following branch of natural science deals with heat and its

transformation to various forms of energy?

• Heat

• Heat Engine

• Temperature

• Thermodynamics

Heat can do work. A device called heat engine is used to make it possible.

Which of the following is a false statement about heat engine?

• Heat Engine converts thermal energy into mechanical energy.

• Heat engine utilizes all thermal energy into useful work due to its 100%

  efficiency.

• Heat engine may be classified into two major types: internal

  combustion engine and external combustion engine.

• Heat engine uses a working substance that cools and/or heats,

  compresses and/or expands like water in a steam engine.

What happens when heat is added to a system?

• The thermal energy will be wasted.

• The thermal energy will increase and can do work.

• The thermal energy will decrease and can do work.

• The thermal energy will increase the temperature of the environment.

Geothermal power plant is a way to harness the thermal energy coming

from the Earth’s interior and uses heat engine to generate electricity. Which

is not included in the processes that all heat engines follow?

• Some of the thermal energy from the input heat increases the

  temperature in the geothermal power plant.

• The rest of the thermal energy decreases temperature, condenses into

  water and goes back beneath the ground through injection well.

• Heat is added to the engine by a hot reservoir. The hot water produces

  steam that turns turbine which is connected to generator that generates

  electricity.

• Some of the thermal energy from the input heat is used to do useful

  work like turning the turbine connected to generator generating

  electricity

Teacher Cristel is showing flash cards showing examples of heat engines in

your Science class. She asked you to choose which does not belong to the

group. What are you going to pick?

• car

• refrigerator

• motorcycle

• thermal power generator