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

For this tool, system refers to either a complete circuit or one circuit component (e.g., a battery, bulb, or a capacitor), You cannot select an subcircuit. For example, if a circuit consists of a battery, bulb, and capacitor, you can select the battery or the bulb or the capacitor or all three objects. You cannot select the battery & bulb, but not the capacitor; the battery & capacitor, but not the bulb; or the bulb & capacitor, but not the battery.

Place an energy bars tool by first selecting the target system, 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.

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. Choose hand mode if you know (or can guess) the maximum energy change that will be displayed during the simulation.
• Maximum value. Hand mode only: Sets the maximum energy value displayed by the bars. In auto mode, setting this value has no effect.

The figure below illustrates the layout of the Energy Changes Bars tool. The bar graph displays the enery changes for a system consisting only of one element, a motor-fan, which is connected to a battery. The bar graph displays the cumulative energy changes for the forty seconds that the motor has been connected to the battery. The Energy Input to the motor-fan is simply the total electrical energy supplied by the battery. The Energy Output by the motor-fan into the surrounding environment is split between two forms of mechanical energy, motion (of the air whipped up by the fan) and sound (generated by the motor), and heat. The Energy Changes in System (i.e., changes in the motor-fan's internal energy) consist of increases in thermal energy (caused by resistive heating) and motion energy (the motion of the fan).