Gravitational Field + Electric Field Flashcards
Newton’s Law of Gravitation
States that two point masses attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
Gravitational Field
A region in space in which a mass placed in that region experiences a gravitational force
Gravitational Field Strength
The gravitational force experienced per unit mass at that point
Shell Theorem
Inside a solid sphere of constant density, the gravitational force varies linearly with distance from the centre, becoming zero by symmetry at the centre of mass.
Gravitational Potential Energy (U)
The GPE of a mass at a point in a gravitational field is defined as the work done by an external force in bringing the mass from infinity to that point
Gravitational Potential (phi)
The GP at a point in a gravitational field is defined as the work done per unit mass by an external force in bringing a small test mass from infinity to that point.
Escape Velocity
The minimum speed needed for the object to just escape from the gravitational influence of a massive body
Conditions for Geostationary Orbit
Centre of Earth coincides with the centre of orbit of the object/satellite
Axis of rotation of the Earth coincides with the axis of orbit of the object/satellite
The object/satellite orbits from West to East
The period of one orbit of the object/satellite is 24 hours.
Why is GP/GPE negative in value
GP/GPE at ∞ is zero.
Since gravitational force is attractive in nature, to bring a mass from infinity to a point in the gravitational field, the direction of the external force is opposite to the direction of displacement of the mass.
This results in negative work being done by the external force
Coulomb’s Law, F = qE = -dU/dr
States that the force between two point charges is proportional to the product of the charges and inversely proportional to the square of the distance between them
Electric Field
An electric field is a region of space in which a charge placed in that region experiences an electric force
Electric Field Strength, E = F/q = -dV/dr
The electric field strength at a point in an electric field is the electric force exerted per unit positive charge placed at that point
Electric potential, V = Er
The electric potential at a point is defined as the work done per unit positive charge by an external force in bringing a small test charge from infinity to that point
Electric potential energy, U = qV
The work done by an external force in bringing the charge from infinity to that point
Criterion for an electric field to be considered uniform
The electric field strength at any point has the same magnitude and direction and the equipotential lines are parallel and equally spaced
