Topic 3.0: Devices And Systems Convert Energy

Question 1

Chemical energy

Answer 1

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

Question 2

Electrical energy

Answer 2

Energy of charged particles

Is transferred when negatively charged electrons travel from place to place

Question 3

Mechanical energy

Answer 3

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

Question 4

Thermal energy

Answer 4

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

Question 5

Energy

Answer 5

The ability to do work

Forms: electrical, chemical, mechanical and thermal

Question 6

Energy transformation

Answer 6

Input energy and output energy

Ex. Toaster- electrical to thermal

Question 7

Thermocouple

Answer 7

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

Question 8

Practical uses of thermocouples

Answer 8

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

Question 9

Polarity

Answer 9

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

Question 10

Faradays device

Answer 10

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

Question 11

Electric motors

Answer 11

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

Question 12

Commutator and brushes

Answer 12

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

Question 13

Armature

Answer 13

Continues to spin because of momentum

It is the rotating shaft with the coil wrapped around it

Question 14

Magnets

Answer 14

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

Question 15

Direct and indirect current

Answer 15

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

Question 16

Electromagnetic induction

Answer 16

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

Question 17

Generating electricity with a DC generator

Answer 17

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

Question 18

Generating electricity with an AC generator

Answer 18

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

Question 19

Generators

Answer 19

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

Question 20

Power

Answer 20

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

Question 21

Calculating energy

Answer 21

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

Question 22

Joules

Answer 22

Used to measure small amounts of energy used

Question 23

Kilowatt hours

Answer 23

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

Question 24

Law conservation of energy

Answer 24

Energy cannot be created or destroyed

Energy doesn’t appear or disappear- it can only be transformed from one form to another

Question 25

Efficiency

Answer 25

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

Question 26

Energy dissipation

Answer 26

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

Question 27

Output energy’s

Answer 27

Thermal
Electrical
Light
Mechanical
Electrical
Sound
Ex: flashlights output- electrical than light and then thermal