3.7.1.1
Radial fields point inward; uniform fields have parallel lines
Gravitational Fields & Orbits — AQA A-Level Physics
- Around a point mass or outside a sphere, field lines are radial: they point inward towards the centre.
- A radial field is non-uniform. The field strength g varies with distance from the centre.
- Near the Earth's surface, the field is approximately uniform. Field lines are parallel and equally spaced.
- In a uniform field, g has the same value at all points.
- A uniform sphere can be modelled as a point mass at its centre. Its external field lines are identical to those of a point mass.
Examiner Tips and Tricks
- Always draw arrows on gravitational fieldA region of space in which a mass experiences a gravitational force. lines pointing towards the mass.
- For a radial field: arrows point towards the centre.
- For a uniform field: arrows point towards the surface (downward near Earth).
- Marks are lost for missing arrows.