Questions where students often pick the tempting wrong answer — make sure you know the right one:
In which direction does an electric field point near a positive charge?✗ Radially inwards because positive attracts negative.✓ Radially outwards — the field is defined by the force on a positive test charge, which is repelled.
What does gravitational field strength at a point represent?✗ The total gravitational force at that point regardless of mass.✓ The force per unit mass that would act on a test mass placed at that point.
If the distance between two masses doubles, what happens to the gravitational force between them?✗ It halves — gravitational force is inversely proportional to distance.✓ It quarters — gravitational force is inversely proportional to the square of the distance.
Why is gravitational potential energy near a planet treated as negative?✗ Gravitational potential energy is negative because gravity always points downwards.✓ Because the zero is defined at infinity; objects bound to the planet have lower (negative) potential energy than at infinity.
What does the spacing of field lines on a diagram indicate?✗ Field lines are equally important regardless of spacing — only the arrows matter.✓ The strength of the field — closer lines mean a stronger field.
Practise Fields — free games
Test yourself with these quick revision games for this topic:
