#### hazim

Joined Jan 3, 2008
434
Hi. I have two independent questions:

1- In a k-map, if all cells are don't care, will F be 1 or 0 or any (we don't care)?

2 In a circuit, there is a capacitor and the value is written like this: 25/6 uF; is the value 25 divided by 6 (as my instructor said) or it's 25V 6uF?

Thank you.

#### mentaaal

Joined Oct 17, 2005
451
In answer to your first question, if all the cells are dont care, then, as the name suggests, you dont care. F can be either 1 or 0.

Regarding your second question, sorry i dont know but i would guess the latter??

#### scubasteve_911

Joined Dec 27, 2007
1,203
It would be silly to write a fraction that results in a whole number, so it must be another parameter of the capacitor. When designing my circuits, I indicate unobvious needs for higher wattage or voltage rated parts next to the value. So, it probably is 25V, especially if the circuit supply to the component is < 18V

Regarding K-maps, the X states, when used properly, greatly simplify logic. Be sure to care about them

Steve

#### hazim

Joined Jan 3, 2008
434
I see my instructor not skilled..in the final exam i had that 25/6 capacitor, i asked him during the exam after i solved the problem as 25V 6uF but he said that it's 25 divided by 6...i said to him as you say scubasteve that it would be silly to write a fraction that results in a whole number....and about the k-map, there is nothing to simplify, all cells are X, i agree with mentaaal

#### scubasteve_911

Joined Dec 27, 2007
1,203
I was trying to say that you can often use 'dont-care' states to simply logic by taking them as 0s and 1s where you may need them.

You learned an important lesson in life during the exam. Don't assume for yourself, ask for clarifications.

Steve

#### hazim

Joined Jan 3, 2008
434
You learned an important lesson in life during the exam. Don't assume for yourself, ask for clarifications.

Steve
sure, but in this case as i said..that instructor is.....not knowledgeable

#### scubasteve_911

Joined Dec 27, 2007
1,203
Well, if the professor thinks it is a fraction and he is marking the exam, then just follow through. When writing exams and things are unclear, don't be afraid to write your assumptions.

Writing something like "I am assuming that 25/6 uF means that the capacitor has a value of 6uF and a rated voltage of 25V". You should be marked upon the process, not silly details such as an ambiguous value.

Steve

#### kubeek

Joined Sep 20, 2005
5,768
Since when is 25/6 a whole number?
And I think the value is 25uF/6V.