| q E |
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| m |
What is a field? What is an example of a field? Why is a field useful?
A field is something that has a magnitude and direction at all points in space.
A good example is the Earth's gravitational field. Drawing the field helps us visualize how an object, through its mass, influences the region around it.
An electric field can help us visualize how an object, through its charge, or how a collection of charged objects, influences the region around it.
In a uniform gravitational field F = mg
Applying Newton's Second Law tells us that mg = ma, so a = g.
In a uniform electric field F = qE
If gravity can be neglected applying Newton's second law gives:
| qE = ma, | so | a = |
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An example of a non-uniform field is the gravitational field from an object of mass M:
| g | = | – |
|
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Similarly, the electric field from an object of charge Q is:
| E | = |
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