What enables hydroelectric power plants to keep up with spikes in demand for electricity?
O a
Ob
generators that are controlled
Dams that open and close
stations that can be turned off and on
all of the above

Agroup of students is studying convection current. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other is in an area with warm air. after 10 minutes, the balloon are released from a height of 1 meter. which of the following to the students most likely observe? a) the warm balloon expands and rises. the cold balloon shrinks and sinks b) the balloon both rise. the cold balloon is larger than the warm balloon c) the cold balloon expands and rises. the warm balloon shrinks and sinks d) the balloon rise at the same rate. both balloons are the same size

Light waves can move through , but they travel fastest when they move through a(n) .

How can the number of core electrons be determined from the periodic table