Topic 3.0: Devices And Systems Convert Energy Flashcards Preview

Flashcardlet decks > Topic 3.0: Devices And Systems Convert Energy > Flashcards

Flashcards in Topic 3.0: Devices And Systems Convert Energy Deck (27):

Chemical energy

Sugar contains this energy
The cells in our body use glucose (sugar) molecules in a series of chemical reactions to produce thermal and mechanical energy


Electrical energy

Energy of charged particles
Is transferred when negatively charged electrons travel from place to place


Mechanical energy

The energy an object has because of its motion or potential to move
A thrown baseball has mechanical energy because of its movement and its potential to fall


Thermal energy

Total kinetic (energy of motion) of all the particles in a substance
The faster a particle moves the more kinetic energy it has



The ability to do work
Forms: electrical, chemical, mechanical and thermal


Energy transformation

Input energy and output energy
Ex. Toaster- electrical to thermal



Transforms thermal energy into electrical energy
Made of two different metals that are joined together which conduct hear at different rates
When heated the difference in conduction results in electricity flowing from metal to the other


Practical uses of thermocouples

Car engines- temp in a car can be extreme and the reading may come from deep in the engine
A thermocouple can withstand these high temps because it generates electrical energy that can gauge from the thermocouple sensor for convenient temp readings



Refers to the condition of having north or south ends such as in a permanent magnet


Faradays device

He constructed a device that used electromagnetic forces to cause an object to move around a magnet
This eventually led to the development of the electrical motor
He also demonstrated that electrical current is created in a wire that moves a magnet field which lead to the modern electric motors
Generators create electrical current


Electric motors

Reversing the current reveres the polarity of an electromagnet thereby keeping it spinning
Use a commutator, brushes, armature, magnets and coil


Commutator and brushes

Reverse the flow of electricity through the electromagnetic coil
Commutator- split ring that breaks the flow of electricity for a moment and then reversed the connection of the coil
Brushes- bars of carbon pushed against the commutator by springs
They make electrical contact with the moving commutator brushing against it



Continues to spin because of momentum
It is the rotating shaft with the coil wrapped around it



They can be adjusted to alter the speed of the spinning coil by being closer or farther away from the coil
Attractive and repulsive forces make the coil turn
Allowing the commutator to change position so it's one side touches the brush


Direct and indirect current

DC: current flows in only one direction- positive terminal to negative terminal
Alternating current AC: current flows back and forth, alternates direction

Transforms change the amount of voltage without energy loss
Voltage change is necessary because the most efficient way to transmit current over long distances is at high voltage


Electromagnetic induction

It generates electricity by demonstrating that electrical current could be generated by moving a conducting wire through a magnetic field


Generating electricity with a DC generator

If you run electricity through a DC generator it will spin like a motor she to the armature producing electricity
Has a different axel than the AC generator


Generating electricity with an AC generator

The central axel of an AC generator has a loop of wire that is attached to 2 slip rings... Than current is generated in the wire through passing a magnetic field.
Current switched back and forth in the wire when it does a complete turn around the loop
Brushes and slip rings allow it to spin freely and operate on its axel that is different to the DC generator



They create electrical current rather than store it... It stores gasoline for the electrical current and if it runs out it won't work.



The rate at which a device converts energy
Unit of power: watt
P: current multiplied by voltage
Current: p divided by v
V: p divided by current
Identify known and unknown quantities
Use the correct formula
Solve problem


Calculating energy

E: power times time
Times by 60 sec for the minutes times 2
Divide to the 2nd decimal point to get MJ



Used to measure small amounts of energy used


Kilowatt hours

Often used to measure small amounts of energy like joked but it doesn't take long for appliances to consume large amounts of energy
W divided by 1000 times 100


Law conservation of energy

Energy cannot be created or destroyed
Energy doesn't appear or disappear- it can only be transformed from one form to another



Efficiency of a device is the ratio of the useful energy that comes out of the device to the total energy that went usually calculated as a percent
Joules of output divided by joules of input times 100


Energy dissipation

Energy cannot be created or destroyed therefore missing energy is lost as heat energy
Mechanical systems also dissipate energy to their surroundings
For example: a pump looses some of its energy as sounds and heat from the friction


Output energy's

Ex: flashlights output- electrical than light and then thermal

Decks in Flashcardlet decks Class (34):