What is the largest-aperture earth-based telescope currently in use at visible wavelengths?

The density of a liquid could be found by using

How do the measurements of charge at the different locations on the sphere compare to each other? the charge measurements are different at all locations on the sphere. the charge measurements are virtually not the same at all locations on the sphere except for the charge at the very top and at the very bottom that are equal. the charge measurements are virtually the same at all locations on the sphere except for the charge at the very top. at the top, the conductive sphere has a small disk that is made of different material. the charge measurements are the same at all locations on the sphere. what happens to the charge on the conductive sphere when it is connected to a source of charge such as the electrostatic voltage source? nothing will happen because no charge goes around the surface of the sphere. the charge on the conductive sphere spreads out over the surface of the sphere; being greater in some specific locations on the sphere. the charge on the conductive sphere spreads out uniformly over the surface of the sphere. the charge on the conductive sphere spreads out non-uniformly over the surface of the sphere.

Which of the following changes will result in a stronger electromagnet? a. using fewer coils of wire b. using a higher voltage c. using a shorter nail d. using a longer wire