Suppose that the original resistor is replaced by a resistor of the same physical dimensions but made of a material that has half the density of charges to carry current, but each carrier has double the charge of those in the original resistor. Further suppose that the potential drop across the resistor is the same as for the original The current through the new resistor will be:. a. Twice as big as for the original resistor.
b. The same as for the original resistor.
c. Half as big as for the original resistor.
d. You can’t tell from the information given.
e. Some other multiple of the original current.

Spend time observing or thinking about events that involve matter and energy. which events can you explain? which events can’t you explain?

Air initially at 0.75 bar, 1000 k, and occupying a volume of 0.12 m^3 undergoes two processes. process 1-2: the air is compressed isothermally until the volume is halved. process 2-3: the air undergoes a constant pressure process until the volume is halved again. assume ideal gas behavior. a) determine the mass of the air, in kg. b) the work and the heat transfer for each of the two processes, in kj. (100 kj = 1 bar . m^3)

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.