Energy Changes Bars Tool: The Energy Changes Bars Tool plots colored bars that display the energy put into the gas container, the energy put out by the gas, and the energy changes within the container. This tool only plots in Run mode.

Place an energy bars tool by first selecting the container (don't select the heater/cooler) then clicking on the Energy Bars button, and finally clicking at the desired position of the bar graph. You can later reposition the energy bars graph. Warning: This tool will not work if a gas tank or a vacuum pump is attached to the container.

In the energy bars tool's Properties Box, you can set:

• Refresh time. How often the tool redraws the energy bars. The default value is 0.2 sec. The shortest refresh time, 0.1 sec, means the energy bars have the same temporal resolution as the clock. However, at such a short refresh time, energy readouts are difficult to read.
• Show energy readouts. Controls whether energies are displayed as numbers as well as bars. Default option is to display the readouts.
• View mode. Determines the size of the Energy Changes Bars display. You have three choices, min mode, normal mode, and max mode. Normal mode, displayed below, is the default. Energy labels and readouts are not visible in min mode.
• Scale mode. You have two choices, auto mode or hand mode. For descriptions of these two modes and what you need to consider in making the choice, see Choosing Scale Mode on the graph tool's help page.
• Maximum value. Hand mode only: Sets the maximum energy value displayed by the bars. In auto mode, setting this value has no effect.

This figure illustrates the layout of the Energy Changes Bars tool. The bar graph displays the energy changes for a container filled with nitrogen. The bar graph displays the cumulative energy changes for the 48 seconds that the heater has been turned on.
The Energy Input to the container is simply the total heat energy supplied by the temperature control unit (i.e., heater/cooler). The Energy Output by the expanding nitrogen gas to the piston is the mechanical energy of the piston's motion. The Energy Changes in System consists of an increases in the temperature energy of the nitrogen gas.