What determines the direction of an electric field?

The direction of an electric field is determined by the charge of the source particle that creates it.

In more detail, an electric field is a region around a charged particle within which a force would be exerted on other charged particles. The direction of the electric field is always directed away from positively charged particles and towards negatively charged particles. This is a convention in physics to indicate the direction in which a positive test charge would move if placed in the field.

The strength and direction of the electric field are represented by electric field lines. The denser these lines, the stronger the electric field at that point. The direction of the field is shown by the direction of the lines. For a positive charge, the electric field lines radiate outwards, indicating that a positive test charge would be repelled away from the charge. For a negative charge, the field lines point inwards, showing that a positive test charge would be attracted towards the negative charge.

It's important to note that the electric field exists regardless of whether there is a test charge present to experience the force. The field is a property of the charged object that created it. The direction of the electric field at any point in space is the direction of the electric force that would be exerted on a positive test charge placed at that point.

In summary, the direction of an electric field is determined by the charge of the source particle. It points away from positive charges and towards negative charges, indicating the direction of force a positive test charge would experience.