Comparisons of Electric and Gravitational Fields

Unit 4 - AQA A

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  • Created on: 07-01-13 13:21
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Comparisons: Gravitational and Electric Fields
Similarities:
Gravitational property Electrical property
For the force to act... Contact not needed ­ force Contact not needed ­ force
acts at a distance acts at a distance
Range of field Infinite ­ size of force Infinite ­ size of force
decreases as distance decreases as distance
increases but in theory never increases but in theory never
falls to zero falls to zero
Field lines Can be used to describe the Can be used to describe the
field ­ direction is the direction field ­ direction is the direction
of the force on a mass of the force on a positive
charge
Field strength Defined as the force on unit Defined as the force on unit
mass: charge:
F
g = m E = FQ
Force between two objects Given by Newton's law of Given by Coulomb's Law:
universal gravitation:
Q1Q2
F = GMm r² F = 41

0
(inverse-square law) (inverse-square law)
Potential Can be used to describe the Can be used to describe the
work done in moving masses: work done in moving charges:
V = - GM
r V = kQr
(inverse law) (inverse law)
Potential Energy Gravitational potential energy = Electrical potential energy = QV
mV
Relationship between Field strength is negative of Field strength is negative of
potential and field strength potential gradient: potential gradient:
g = - r
V E = - V
r
Kinetic Energy Calculated from: Calculated from:
1 mv² = mV 1 mv2 = QV
2 2

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Differences:
Gravitational Property Electrical Property
Origin Produced by and act upon Produced by and acts upon
masses charge
Effect Causes attraction only Can cause attraction or
repulsion
Shielding Not possible ­ no material has Possible ­ shielding possible
been found that is able to using devices such as Faraday
shield gravitational forces Cages
Comparative size Insignificant unless one or both Much bigger
masses is huge…read more

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