Write two properties of equipotential surfaces.

Explanation

### Step-by-Step Solution:

1. **Definition of Equipotential Surface**:
An equipotential surface is defined as a surface where all points on that surface have the same electric potential. This means that no work is required to move a charge along the surface since the potential difference is zero.

2. **First Property**:
The first property of equipotential surfaces is that they are always perpendicular to electric field lines. This means that if you have an electric field created by a charge, the equipotential surfaces will intersect the electric field lines at right angles. For example, if you have a point charge, the equipotential surfaces around it will be spherical, and the electric field lines will radiate outward from the charge, intersecting the equipotential surfaces perpendicularly.

...