Final answer:
The electric field strength just above one face of a copper penny depends on its charge and surface charge density, which directly requires more information to calculate, using the formula E = σ / (2ε_0) for a charged conducting sheet.
Step-by-step explanation:
The electric field strength just above one face of a copper penny can be considered similar to the electric field near a conducting plate. If the penny were to be charged, using the concept of electric fields near conductors, the electric field just above the surface would be perpendicular to the surface of the penny. However, without specific information regarding the charge on the penny or potential difference, we cannot calculate the electric field strength directly. For example, consider the scenario where a thin conducting plate of 2.0 m on a side is given a total charge of -10.0 µC; in such cases, we can calculate the electric field a certain distance from the plate using the formula for electric field due to a charged infinite sheet: E = σ / (2ε_0), where σ is the surface charge density, and ε_0 is the permittivity of free space.