Download 1 - Field Strength Notes Handout

30/04/2017
Science 30 Unit C – Physics:
Field Theory
Name: ________
Date: ________
Force: Definition: ___________________________________________
What are some forces you can think of?
4 Fundamental Forces
Every force in the universe fits into one of 4 basic groups:
Have you ever thought why these force work? Why does gravity make objects fall to the ground?
Why do balloons rubbed on the top of your head stick to the wall? Why do magnetics pick up
paper clips, and how does an electromagnet work?
Fields - one way of explaining _________________________________________
The Gravitational Field
Invisible gravitational fields surround ___________________ at all times.
Every _________ in the universe creates its own gravitational field.
Fields are represented by ________________, which are vectors. The
vectors extend _________ and always point towards the centre of objects.
The ____________ the field lines are together, the ______________ the
field.
Experimentally, it has been found that the strength of the gravitational
field is directly proportional to the mass of the object creating the
field. This means that the __________ the mass producing the
gravitational field, the _________ the field strength.
It was also found through experimental means that the value was also
inversely proportional to the square of the distance between the test
object and the gravity producing object.
We can combine these findings to make a formula for gravitational
field strength:
The value of G was calculated by Cavendish to
be ______________________________.
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This value is quoted on your formula sheet and is _____________ everywhere in the universe!
Also remember that this is an exact value and is not subject to sig-digs.
ex) Calculate the gravitational field strength
on the surface of the Earth.
ex) Calculate the gravitational field strength
on the lowest point of the Marianas Trench
(11034 m below the surface of the earth).
ex) Calculate the gravitational field strength
on the highest peak of Everest (8848 m
above the earth).
ex) Calculate the gravitational field strength
on the International Space Station (about
400 km above the earth).
Enough with gravity, for now. How can we explain the basic principles of the electric force?
The Electric Field
•All electrically _____________ objects (can be
positive or negative) create electric fields.
Electric Charge - Charge is given the symbol q and
is measured in _____________ (C).
As 1 C of charge is actually quite a large amount, we
often deal in millicoulombs (mC) or microcoulombs (μC).
The magnitude and direction of fields are
represented by field lines. The greater the
___________ of the lines, the _________
the field.
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The electric field is in the direction a _______
test charge would move when placed in the
field.
This means that E-fields move __________
positive charges and __________ negative
charges.
Now that we know how to find the direction of an electric field, we need to figure out how to
determine the strength of the field.
ex) Find the electric field at point P.
ex) Find the electric field at point P.
Magnetic Fields - The direction of the force of magnetism can be
explained through field theory.
- All magnets produce a magnetic field (symbol, B)
- The direction of the field is the direction a test compass would point.
- The closer together the field lines, the stronger the field.
- field lines point out of North poles, into South poles
Practice: Field Theory Calculations WS
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