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USING A CALCULATOR

The instructions are for the Casio FX-991ES/991EX or similar. To do complex
operations, the calculator must be set in complex mode. Press the mode button and
then press "2" for CMPLX.

MEMORY STORAGE

Often when doing complex number calculations, you will get an intermediate answer
that you need to use again in the calculation. An easy way to do this is to store the
complex number in one of the calculator's memories. The 991ES (and most other
calculators) have memories A-F and numbers can be stored in complex form with
SHIFT STO A-F, where A to F is the required memory location. If you want to recall
a number from memory A to include it in a further calculation, you only have to press
RCL A.

Find the impedance of Figure 41-22. This is a series circuit with three impedances,
so we must sum the three impedances in complex form.

Zt=Z1+Z2+Z3
Zt=(0+1256.64i)+(0-318.31i)+(1000+0i) {written the way it is keyed into the
calculator}.
Press=
Display shows 1000+938.33i
We normally write this as 1000+j938.33Ω

This means: 1000 ohms of resistance in series with 938.33 ohms of inductive
reactance. This is the impedance of the circuit shown in 41-22 in rectangular form.

If we wanted polar form, we can force the calculator to polar with SHIFT SETUP then
3 for CMPLX and 2 for polar and we get 1371.23/43.17°.

This means the magnitude of the impedance of Figure 41-22 is 1371.23 ohms with
a lagging phase angle of 43.17 degrees.

That was fairly easy, and you may have guessed the answer knowing that when you
have two opposite reactances in series, the net reactance is simply the difference
between the reactances or X=1256.64-318.31 = 938.33Ω and that the R of 1000 is
just tagged on to give 1000+j938.330

What if the three impedances in 41-22 were in parallel? See Figure 41-23

With the three impedances now in parallel, we cannot just sum them. We have to
calculate the reciprocal of the sum of the reciprocals of each impedance.

CASIO calculators working in complex mode receive a complex number input as
(real +/-imaginary).
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