Science: Lesson 3
Describe a Series circuit
-All parts are connected in a row that forms one path for the electric charges to follow -Current is the same for all loads -One bulb burns out-->circuit opens-->charges can't flow-->all bulbs go out
What is a common energy source for a circuit?
A battery
What do fuel cells, batteries, and solar cells have in common?
All sources of DC
Describe DC
Always flows in same direction -Generated by batteries (flashlights, cars, cameras)
Where does a compass point and why?
Always point North b/c the South pole of metal inside compass is attracted to Earth's North pole
Where does a magnetic field occur in relation to an electrified wire?
Around the entire length of the wire
When an electric current runs through a wire, a magnetic field is induced _______?
Around the wire
Which of the following atoms is considered neutral?
Atom with 5 protons and 5 neutrons
Why is static electricity not useful as a power source?
Because all energy is released at once in static electricity
Magnetic force
Bring two magnets together-->exert a push or pull on each other
Transformers
Device that relies on electromagnetic induction-->uses induction to increase or decrease the voltage of AC
Load
Device that uses electrical energy to operate
Describe Fields
Earth's inner structure produces its magnetic field --Charged particles move in the liquid and form a magnetic field-->constant rotation keeps Earth magnetized
What is the relationship between electricity and magnetism?
Electricity is a form of magnetism
Lightning is a form of static electricity. What can you infer about what happens when lighting strikes the ground?
Electrons are transferred from the clouds to the ground
What causes the shock you receive when you touch a doorknob?
Electrons being pulled from one surface to another
Magnetic poles
Ends of magnets (N or S)
What are the three components of a circuit?
Energy source, conductor, and receiver
Which of the following is a true statement?
Faraday built on Orsted's discoveries to describe electromagnetic induction
Define current.
Flow of electrons (HOW FAST) -measured by how many electrons pass a point during each second (amp, A) -AC: comes from outlet; different directions -DC: comes from battery; one direction
Which of the following devices is most likely to contain an electromagnet? -Stove, flashlight, fridge, watch
Fridge
You're going camping, and you need a source of electric current. So, you guy a gasoline powered ___.
Generator
Aurora
Glow of particles interacting with atoms in the air-->cause visible light
How do you read electric meters?
Go clockwise or counterclockwise -Go with lower number (arrow between 6 and 7, go with 6)
How are the magnetic domains of a magnet different from the domains of an ordinary piece of metal?
In a magnet, the domains all point in the same direction; in the ordinary piece of metal, they're all jumbled up
How is variation measured?
In degrees
If you have an electromagnet, how can you make its magnetic field stronger?
Increase the strength of electric current
What can you infer about magnetic domains from the fact that they are arrangements of atoms
Individual domains are extremely small
Which of the following metals can be magnetized?
Iron
Electromagnet
Iron core wrapped around with electrical wire -Made by wrapping a solenoid around an iron core-->Combines magnetic field of solenoid with magnetic field of magnetized iron core
What can you infer about iron from the fact that most compass needles are made from it?
It can be easily magnetized
What are electrons?
Negatively charged subatomic particles
When does a compass needle point south?
Never; a compass needle always points north
What are the two poles of a magnet called?
North and South
Grounding
Providing a path that allows charges to flow into the ground
What role does adhesion play in static electricity?
Pulls electrons from one surface toward another
Electromagnetism
Relationship between electricity and magnetism -->happens when electric currents and magnetic fields interact with each other
What can you infer about this source of electricity?
Source of AC
Magnetic field
The area surrounding a magnet where magnetic forces can be detected
Static Electricity
The buildup of electric charge on an object
Two electromagnets contain the same types of magnets and wires. But the magnet in the first moves much faster than the second. Therefore ________
The first electromagnet has a more powerful current than the second
Why does a compass needle point in the direction it does?
The needle lines up along Earth's magnetic field
How could you use a compass to travel due west?
Travel in the direction 90 degrees to the left of where the needle points
Describe Friction
Two objects rubbing together-->Causes transfer of electrons between objects
Electric Generators
Use Induction to change mechanical energy into electrical energy
Electromagnetic induction
Using a magnetic filed to create an electric current in a wire
How does a generator create current?
Using an electromagnet
When will a circuit breaker trip?
When a very strong current passes through it
Which of the following are sources of mechanical energy?
Wind and fossil fuels
Describe a Parallel Circuit
-Electric charges have more than one path that they can follow -Loads are connected side by side-->any bulb can burn out without opening the circuit -Can have different currents-->All loads experience same voltage
Describe Domains
-Groups of atoms form tiny areas called domains -N and S poles of atoms in domain line up and make strong magnetic field -Domains point toward same direction-->form magnetic field --In other materials, there are no domains to line up b/c atoms have no magnetic fields
What is the purpose of the Van de Graaff generator?
-Places charge on dome -Uncharged object touches dome-->Becomes charged by contact
How do electromagnets differ from regular magnets?
-They can be turned on and off -Their polarity can be reversed -Their strength can be changed
What is a solenoid?
A coil of wire that carries an electric current, producing a magnetic field -more loops=stronger magnetic field
Solenoid
A coil of wire that carries an electric current, producing a magnetic field-->more loops=stronger magnetic field
Electric circuit
A complete, closed path through which electric charges can flow-->Form a loop
A flow of electrons through a conductor is called _____?
A current
Galvanometer
A device that measures the strength and direction of an electric current in a wire-->contains electromagnet
What causes lightning?
A difference in electrical charge
Which of the following devices is most similar to a compass?
A global positioning system
What happens when electricity flows through an object?
A magnetic field is created
Electrical conductor
A material through which charges can move freely
Electrical insulator
A material through which charges cannot move easily
If a substance has an excess number of electrons on its surface, what type of charge does it have?
A negative charge
What does the earth have in common with a bar magnet?
A north and south pole
Describe Force
A push or pull exerted on an object in order to change the motion of the object; force has size and direction
What do you need to build a working electric motor?
A source of electricity
Semiconductor
A special class of materials that conduct electric charge better than insulators but not as well as conductors
What device opens and closes an electric circuit?
A switch
Define Induction
A way of rearranging the charges within an object without touching it
Voltage
Amount of work required to move each unit of charge between two points-->expressed in volts (V)-->sometimes called electric potential
What is static electricity caused by?
An imbalance of positive and negative charges
Which term best describes a compass? -A complicated device, a device that's difficult to use, an unsophisticated device, an ornate device
An unsophisticated device
Define Electric Force
Any two charged objects exert a force on each other
Place these events in sequence: A) Voltage decreased by transformer B) Voltage increased by transformer C) Electrical current enters home
B, A, C
How can you create a magnetic field?
By running a current through a wire
Electric motor
Changes electrical energy into mechanical energy-->Runs on AC or DC
What is the function of every generator on Earth?
Changing mechanical energy into electrical energy
Describe Conduction
Charged object and uncharged object touch-->charged object transfers charge to touched area
Electric discharge
Charges that build up as static electricity leaving the object
How is the compass affected by the Earth?
Compass is affected by earth's magnetic field
Why are paperclips attracted to magnets?
Contain iron
In physics, to "induce" something is to _____?
Create it
What is the major difference between static electricity and current electricity?
Current electricity involves a flow of electrons; static electricity involves a single transfer of electrons
How does AC differ from DC?
DC flows in same direction; direction of AC switches back and forth
Amperes
Electric current expression-->Symbol is A
Electric Energy
Energy of electric charges
How might life be different if we didn't have compasses?
European explorers might never have made it to North and South America
Where might you find an electromagnet?
In an electric motor
What can you infer about any object that gives you a tactic shock when you touch it?
It's a conductor
What does a magnetic field look like?
It's invisible
What is the simplest requirement for an electromagnet?
Length of electrified wire
Magnet
Material that attracts iron or objects made of iron
Ferromagnetic
Material that can be turned into a magnet
In most electrical circuits, the pathway is made of _____?
Metal
What happens when you touch a metal doorknob after rubbing your shoes on the carpet?
Millions of electrons go from your finger into the doorknob
What is one possible reason why it's a good idea to conserve electricity?
Often produced by burning fossil fuels, which are a polluting, non-renewable resource
Define resistance.
Opposition to flow of electricity -Good conductors have low electricity -Depends on temp, length, and thickness of wire -Measured in Ohms
Resistance
Opposition to the flow of electric charge-->expressed in ohms
Why would the domains of a paperclip line up?
Paperclip has been exposed to a magnetic field
Define Electric Charge
Property that leads to electromagnetic interactions between the particles that make up matter
How are electrons different from protons and neutrons?
Protons and neutrons exist inside atomic nuclei; electrons orbit atomic nuclei
What is the function of a power source in a circuit?
Provides a steady flow of electrons
Describe AC
Repeatedly changes directions -Comes from outlets (toasters)
What effect will the north pole of one magnet have on the north pole of another magnet?
Repulsive
To change the polarity of an electromagnet, you would ____?
Reverse the current's direction
How does rubber differ from most metals?
Rubber is a good insulator; most metals are good conductors
What is the main function of a turbine?
Spinning
What is a current?
Steady flow of electricity
Which word best describes electricity as it occurs in nature?
Sudden
Which of the following materials is an insulator? -Foil, sweater, coin, or pool flotation thing
Sweater
Define Ion
The atoms overall positive or negative charge
How would you compare the magnetic field generated by a simple length of wire to the magnetic field generated by a coil of wire?
The coil generates a stronger magnetic field
What is variation?
The difference between where a compass points and the Geographic North Pole
What might happen if transformers didn't exist?
The electricity in your house might have an extremely high voltage
What happens if you disconnect a circuit from its positive terminal?
The electrons stop flowing, and the current stops
Electric current
The rate of flow of electric charges
What does lightning have in common with the shock you receive when you touch a doorknob?
They're both forms of static electricity
How does electricity travel from power plants to your house?
Through transmission wires
How might an electric motor be used in a washing machine?
To make the machine spin
Which of the following is an example of a load? -Outlet, battery, toaster, circuit
Toaster
Describe Induction
Way of rearranging charges within an object without touching it
What might happen if wires weren't insulated?
We'd be in danger of harm from electric shocks
Define voltage.
measure of push applies to force electrons to move through a circuit (HOW MUCH IS BEING PUSHED) --Also called potential difference Higher the voltage, the more energy each electron carries and the more work it can do
