# Comparisons of Electric and Gravitational Fields

Unit 4 - AQA A

- Created by: Amy
- Created on: 07-01-13 13:21

First 271 words of the document:

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

r²

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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