Instructions: This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
Input: Passage: The simplest model capacitor consists of two thin parallel conductive plates separated by a dielectric with permittivity . This model may also be used to make qualitative predictions for other device geometries. The plates are considered to extend uniformly over an area A and a charge density = Q/A exists on their surface. Assuming that the length and width of the plates are much greater than their separation d, the electric field near the centre of the device will be uniform with the magnitude E = /. The voltage is defined as the line integral of the electric field between the plates Question: What equation describes the charge density for an ideal model of a capacitor?
Output:
= Q/A