Explain why two negatively charged spheres, held close together but not touching, experience a repulsive force between them. Include in your answer what an electric field is and how the field lines around each sphere are arranged.

An electric field is a region of space in which a charged object experiences a non‑contact force.

Each negatively charged sphere creates its own electric field that extends into the surrounding space.

Because the charge is negative, the field lines point radially inward, towards the centre of each sphere.

When the spheres are close together, their fields overlap. The inward field of one sphere exerts a force on the charge of the other sphere.

Since both spheres carry like (negative) charge, the force on each sphere is directed away from the other sphere, producing a repulsive force.