Why does placing a lid over a pot of water on a stove shorten the time it takes for the water to come to a boil, whereas, after the water is boiling, the use of a lid only slightly shortens the cooking time?

The electric potential v is constant everywhere within a certain region of space. which statement below is true? the choices are: the electric field is also constant (but not zero) within the region. a charged particle placed within the region will experience an electric force. the electric field is zero everywhere within the region. the electric field varies from place to place within the region.