Excel allows you to apply names to arrays, which will make calculations on a *series* of data easier to understand as well.

Worksheet 03y contains a similar internal energy calculation as we’ve seen the last few sections. Instead of calculating the internal energy for one final pressure, this worksheet is set up for calculations using a series of final pressures. For reference, the formula used for this calculation is:

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First, add names to each of the input cells using the name box – **V**, **P_1** and **k** for the volume, initial pressure and the constant k, respectively.

To assign a name to the array of final pressure values, **select **the entire range. Enter **P_2 **in the name box. This name won’t appear if you select a single cell in the range, only if you select the entire range.

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To calculate the change in internal energy, we’ll use an array formula. Remember, for an array formula, you must first **select all the output cells**. Go to the **formula bar** and enter the formula:

**=V*(P_2-P_1)/(k-1)**

You’ll see that the entire range of values for the final pressure is selected when you type P_2. Note that you’ll get an error if you omit the asterisk.

Because it’s an array formula, use **Ctrl-Shift-Enter **to complete the formula. It will fill the energy column with values. You’ll now have an easy-to-read formula if you click any of the cells in the array.

[Note: Want to learn even more about advanced Excel techniques? Watch my free training just for engineers. In the three-part video series I'll show you how to easily solve engineering challenges in Excel. Click here to get started.]