Suppose that the emf from a rod moving in a magnetic field was used to supply the current to illuminate a light bulb in a circuit, and the force needed to keep the rod moving is . What happens to the force needed drive the motion of the rod if the light bulb is removed?a. No force is neededb. there is no longer a magnetic force to oppose the motion. c. It is the same as when the bulb is in the circuit. d. A larger force is needed to the keep the rod moving

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? question 2 options: the balloons rise at the same rate. both balloons are the same size. the ballons both rise. the cold ballon is larger than the warm balloon. the cold balloon expands and rises. the warm balloon shrinks and sinks. the warm balloon expands and rises. the cold balloon shrinks and sinks.