Unit B Energy Flow in Technological Systems : Section 3.0 Flashcards
What is a system?
Objects or objects involved in energy transfers
What is an open system?
A system that exchanges both matter and energy with its surroundings. Eg. Earth
What is a closed system?
A system that cannot exchange matter but can exchange energy with its surroundings. Eg. A can of soup
What is an isolated system?
One that cannot exchange either matter or energy with its surroundings
What does work involve the movement of?
Matter from one location to another
What does heat involve the movement of?
Thermal energy from one location to another
What are the two ways a system can gain energy?
- Heat can be added to the system from surroundings
- Work can be done on a system from its surroundings
What is positive work?
Work done on a system by its surroundings, because the energy of the system increases
What are the 2 ways the energy of a system can decrease?
- Heat can flow out of a system from its surroundings
- Work can be done by system on its surroundings
What is negative work?
Work done by a system on its surroundings because the energy will decrease
What is the first law of thermodynamics?
The total energy, including heat, in a system and its surroundings remains constant
What will an ideal machine do?
- All the input energy is converted into mechanical energy. without any energy loss
- the amount of the mechanical energy produced by the machine should equal the amount of energy put into the machine
- Operate indefinitely
What is the second law of thermodynamics?
Heat always flows naturally from a hotter object to a colder object, but never naturally from a cold object to a hot object
What is a heat engine?
A device that converts heat into mechanical energy. Only some of the heat can be converted into mechanical energy. The remaining is expelled as exhaust heat.
What are heat pumps?
Devices that use mechanical energy to transfer heat
How does a thermo-electric converter fan work?
One end of metal is placed in hot water and the other end is placed in cold water. As heat flows through the metal to the colder end the thermal energy is converted into electrical energy which the fan converts into mechanical energy
What are some of the simple machines?
- Lever
- Pulley
- Wheel and Axel
- Screw
What were the original sources of energy for machines? List four.
- humans
- animals
- wind
- water
What was the first machine to use “hidden energy”
Hero’s Steam engine
What was Hero’s Steam engine?
A novelty device that did nothing useful
What was one of the major problems with coal mines?
Pumping out water
What were the two ways that they pumped water out of coal mines? Then what did Savery invent?
- Archimedes screw
- Persian wheel with the reciprocating pump
Then Savery came up with the steam pump that forces water through pipes (by boiling water with the coal) and can lift water up 6 m.
What were the downsides to the Archimedes screw?
-The water was too heavy to lift
What was the downside to the reciprocating pump?
- Atmospheric pressure can only push water up to height of 9m
- It was limited in the height it could raise water
By who and when was the Gunpowder Engine made?
- 1680
- Christian Hagans (mathematician and physicist)
(gunpowder was invented by the Chinese way before this)
How did the Gunpowder Engine work?
-Christian Hagans used gasses generated by an explosion to drive a piston downwards into a cylinder
What were the drawbacks to Gunpowder Engines?
- Hazards of explosions
- No powerful internal mechanism to pull the pull the piston back up
- Could not operate continuously
What were some scientific discoveries connected with a steam engine?
- The power of vacuums
- Water expands its volume 1300 times when heated to form steam
Who created the earlier heat/steam engine and when was it created?
- Denis Papin
- 1690
How does a Heat/Steam engine work?
- Water is heated so it turns to gas, the gas pushes the piston up
- Water is then pumped on the outside to condense the steam
What were the drawbacks to Heat/Steam engines?
-Manufactures had difficulty producing big enough drums where water could be heated