# two weird question for my power electronics course

#### 6aaron9

Joined Oct 29, 2016
1

anyone know how to solve them?

#### Papabravo

Joined Feb 24, 2006
12,767
These are easy questions and I know how to solve them.

#### crutschow

Joined Mar 14, 2008
24,107
Me too.
But this is homework help, not homework do forum, so you need to show some effort to solve the problem if you expect help from us.

#### Papabravo

Joined Feb 24, 2006
12,767
Me too.
But this is homework help, not homework do forum, so you need to show some effort to solve the problem if you expect help from us.
For part a) do you know what the word "dropout" refers to in the context of this question?

#### AlbertHall

Joined Jun 4, 2014
9,022
The question does seem a little confused on whether the regulator is 7806 or 7805.

#### Papabravo

Joined Feb 24, 2006
12,767
The question does seem a little confused on whether the regulator is 7806 or 7805.
Answer the question both ways. How could that ever be wrong?

#### crutschow

Joined Mar 14, 2008
24,107
The question does seem a little confused on whether the regulator is 7806 or 7805.
The diagram shows a 7806 and states the output voltage is 6V so I would think statement a) has a typo.

And 6aaron9, which two questions do you consider "weird"?

#### Papabravo

Joined Feb 24, 2006
12,767
The diagram shows a 7806 and states the output voltage is 6V so I would think statement a) has a typo.

And 6aaron9, which two questions do you consider "weird"?
His original post, since corrected, had the same question repeated for a total of two identical questions.

#### JoeJester

Joined Apr 26, 2005
4,130
The question does seem a little confused on whether the regulator is 7806 or 7805.
Looks like the typical "copy and paste" error and a lack of due diligence by the professor, as it was their responsibility for the questions asked in their course.

#### dl324

Joined Mar 30, 2015
9,601
The question does seem a little confused on whether the regulator is 7806 or 7805.
I's assume it was 6V because 5V was only mentioned once.

But is the load current 200mA or 300mA; 50-50 chance there...

I'd give the instructor a failing grade for his communications skills.

#### crutschow

Joined Mar 14, 2008
24,107
....
............
What do you need to know?
The only question regarding that is a), which just wants to know the voltage.

#### dl324

Joined Mar 30, 2015
9,601
What do you need to know?
Need to know what the input voltage is. Text said it was variable and unregulated. An equation can be given, but not a number.

#### AlbertHall

Joined Jun 4, 2014
9,022
Need to know what the input voltage is. Text said it was variable and unregulated. An equation can be given, but not a number.
I wondered about that but I presume you would adjust the supply to be just high enough to keep the regulator happy.

#### crutschow

Joined Mar 14, 2008
24,107
I wondered about that but I presume you would adjust the supply to be just high enough to keep the regulator happy.
Yes, from the nature of the question, that was my assumption also.

#### WBahn

Joined Mar 31, 2012
25,096
I wondered about that but I presume you would adjust the supply to be just high enough to keep the regulator happy.
That seems like the most reasonable assumption to make.

The question was clearly not proofread carefully enough -- it was probably a prior question that was recycled by changing a couple values and the person writing it (may or may not have been the instructor) didn't look carefully to ensure that the entire problem was changed consistently. It happens. The best thing for the TS to do is verify what the correct values are with the instructor (who can just choose the values to use even if they didn't write the problem). If that is not an option, then the TS should choose the values they think are most likely the intended ones and make a note regarding the need to make an arbitrary choice and what choices they made.