Solving Currents & Impedance for 50V, 60 Hz Circuit

[EVriderDK]

Homework Statement

50 volts, 60 Hz
http://peecee.dk/upload/view/363429

I have to find the current through R, C, and L.
Total current.
Totalt impedance.

Homework Equations

I=(U/Z)

The Attempt at a Solution

See picture: http://peecee.dk/upload/view/363430

For I_R it must be (50/150)=0.333. And as it is a resistor, the angle must be 0, so 0.333∠0 ?

On my TI89 i can sum all the currents on complex form, but how to do it in mathcad? On the TI89 it is just (3∠90)+(4∠90) etc.

Thank you in advance.

 

[gneill]

Homework Statement

50 volts, 60 Hz
http://peecee.dk/upload/view/363429

I have to find the current through R, C, and L.
Total current.
Totalt impedance.

Homework Equations

I=(U/Z)

The Attempt at a Solution

See picture: http://peecee.dk/upload/view/363430

For I_R it must be (50/150)=0.333. And as it is a resistor, the angle must be 0, so 0.333∠0 ?

On my TI89 i can sum all the currents on complex form, but how to do it in mathcad? On the TI89 it is just (3∠90)+(4∠90) etc.

Thank you in advance.

In MathCad you can work directly with complex numbers. Just assign R, Z_L, Z_C variables the appropriate complex values, then write whatever expressions you want with them. Use the |x| operation to find the magnitude of the complex value x. Similarly use the arg(x) function to find the argument, that is angle, of the complex value.

Examples:

 

[EVriderDK]

Thank you!

Well, I'm trying to do this: http://www.ece.uidaho.edu/ee/power/ECE528/Polar PDF.pdf
But what i get is red markings: http://peecee.dk/upload/view/363597

 

[gneill]

Thank you!

Well, I'm trying to do this: http://www.ece.uidaho.edu/ee/power/ECE528/Polar PDF.pdf
But what i get is red markings: http://peecee.dk/upload/view/363597

The red highlight that you're seeing on the "j" variable indicates that you're referencing an undefined variable.

When entering i or j to represent ##\sqrt{-1}## then enter them as 1i or 1j, that is, a numeric 1 followed immediately by i or j. The '1' will disappear when the equation is not selected. This serves to distinguish these special variables from mundane variables i and j that you may define and use.

 

[EVriderDK]

Thank you! Do you know how only to calculate on polar form?

I want this result as polar, instead of complex: http://peecee.dk/upload/view/363771

And is there away to reset all defined variables? Like r:=r with r and all:=all with all? :)

 

[gneill]

Thank you! Do you know how only to calculate on polar form?

I want this result as polar, instead of complex: http://peecee.dk/upload/view/363771

And is there away to reset all defined variables? Like r:=r with r and all:=all with all? :)

I'm not aware of any built-in way to force a result to be displayed in polar form, at least not with the older version of Mathcad that I'm using.

You can "undefine" individual variable numerical values by using them in unfinished assignment statements:

r :=
b :=

etc.

They can be turned into unassigned variables for the symbolic processor by equating them to themselves as you've done. I'm not aware of any way to de-assign all variables in one step.

 

[EVriderDK]

THank you for all your help!

 

[NemoReally]

Thank you! Do you know how only to calculate on polar form?

I want this result as polar, instead of complex:

You can define functions to do the conversions. In Mathcad 15, you can define them in such a way as to allow you to put them in the unit placeholder to display results in the way you want.



NR

 

[EVriderDK]

Thank you very much again Nemo. That was helpful. Now i can save a couple of steps henceforth ;)