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# There are 2 types of electric charges

### The closer the field lines are to each other, the greater the field’s strength.

From ThePhysicsClassroom website:

App: Electric Field Lines Interactive
http://www.physicsclassroom.com/Physics-Interactives/Static-Electricity/Electric-Field-Lines/Electric-Field-Lines-Interactive

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## What is a compass? How do we use one?

### You can usually figure out which end is which from the position of the Sun in the sky, remembering that the Sun rises in the east and sets in the west. So if you’re looking down on the floating needle at about noon, with the eye on the left and the point on the right, and the Sun in front of you, you know the point is indicating north.

http://www.explainthatstuff.com/how-compasses-work.html

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### One end of the metal needle always points to the North Pole’ the other always points to the South Pole.

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## What is pulling the metal needle in the compass?

### That’s why compass needles are lightweight (so gravity has less effect on them) and mounted on frictionless bearings (so there’s less frictional resistance for the magnetic force to overcome).

http://www.explainthatstuff.com/how-compasses-work.html

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“Where the Earth’s magnetic field comes from, Chris Rowan

### The dynamism that is apparent from the wandering of the magnetic poles with respect to the spin axis (secular variation), and the quasi-periodic flips in field polarity, also suggest that some process is actively generating and maintaining the geomagnetic field. Geophysicists therefore look to the most dynamic region in the planetary depths, the molten outer core, as the source of the force that directs our compass needles…

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## How a planet becomes a magnet

### Earth’s magnetic field single-handedly protects life on this planet from a deadly case of solar wind-burn, By Bernie Hobbs

http://www.abc.net.au/science/articles/2011/11/09/3359365.htm

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### App: The solar wind and Earth’s magnetic field

http://esamultimedia.esa.int/multimedia/edu/PlanetaryMagneticFields.swf

### Learning about Earth’s magnetic field: ESA’s Swarm mission

http://www.esa.int/Our_Activities/Observing_the_Earth/The_Living_Planet_Programme/Earth_Explorers/Swarm/ESA_s_magnetic_field_mission_Swarm

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## How do magnets work?

http://www.school-for-champions.com/science/magnetism.htm#.VSQjudzF9xs

## What is a magnetic field?

### We are surrounded by magnetic fields all the time, but our bodies don’t feel them.  Our nerves don’t detect magnetism.  So how can we see these invisible magnetic lines of force? How do we know that they are real?

Bar magnet surrounded by compasses

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### “A magnetic field consists of imaginary lines of flux coming from moving or spinning electrically charged particles. Examples include the spin of a proton and the motion of electrons through a wire in an electric circuit.”

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## The Earth’s interior generates a magnetic field

This field reaches out into space

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## Learning Standards

Massachusetts 2016 Science and Technology/Engineering (STE) Standards

7.MS-PS2-5. Use scientific evidence to argue that fields exist between objects with mass, between magnetic objects, and between electrically charged objects that exert force on each other even though the objects are not in contact.

7.MS-PS3-2. Develop a model to describe the relationship between the relative positions of objects interacting at a distance and their relative potential energy in the system. {Examples could include changing the direction/orientation of a magnet.}

HS-PS2-1. Analyze data to support the claim that Newton’s second law of motion is a mathematical model describing change in motion (the acceleration) of objects when acted on by a net force….{forces can include magnetic forces}

HS-PS3-5. Develop and use a model of magnetic or electric fields to illustrate the forces and changes in energy between two magnetically or electrically charged objects changing relative position in a magnetic or electric field, respectively.