The direction of the electric field at a point is defined as the direction of the force that a small positive test charge would experience if placed at that point. We will apply this definition to determine the electric field direction due to a positive source charge.
Correct Option: B) Away from the charge
The electric field lines originate from positive charges and terminate on negative charges (or at infinity). Therefore, for a positive charge, the electric field lines point radially outward, i.e., away from the charge.
What is the electric field at a point midway between two equal but opposite charges?
To determine the electric field at the midpoint between two equal but opposite charges, we need to apply the principle of superposition. This involves calculating the electric field due to each charge individually at that point and then adding them vectorially.
B) Non-zero. As derived, the electric fields from both charges add up constructively at the midpoint because they point in the same direction (towards the negative charge), resulting in a non-zero net electric field.
The question asks to identify the quantity that represents potential energy per unit charge. We need to recall the definitions of the given options in electrostatics.
Correct Option: C) Electric potential is defined as the electric potential energy per unit charge. Its unit is Volts (V), which is equivalent to Joules per Coulomb (J/C).
The question asks for the definition of potential difference between two points in an electric field. We need to recall the fundamental definition of electric potential difference from electrostatics.
A) The amount of work done to move a charge from one point to the other. While the precise definition is work done per unit charge, among the given choices, this option best describes the essence of potential difference, which is the energy required (work done) to move a charge in an electric field. The work done is directly proportional to the potential difference and the charge moved (\(W = q \Delta V\)).
The relationship between electric potential difference and electric field is fundamental in electrostatics. The electric field is defined as the negative gradient of the electric potential. Conversely, the potential difference between two points can be found by integrating the electric field along a path connecting those points.
A) It is the integral of the electric field along the path. This statement correctly describes the relationship. The potential difference \(V_B - V_A\) is given by the line integral of the electric field from A to B (with a negative sign, or equivalently, the integral of the negative electric field).
The question asks for the definition of an equipotential surface. We need to recall the fundamental definition of electric potential and how it relates to such a surface.
Correct Option: A) A surface where the electric potential is constant.
This directly matches the definition of an equipotential surface, where "equi" means equal and "potential" refers to electric potential. Therefore, it is a surface where the electric potential is the same at all points.