I ran across this ages ago, and I present it to each new electronics class as an exercise.

You have a black box with four leads coming out of it. You apply a voltage (ac or dc) to any two adjacent leads. The two remaining leads output precisely 1/4 of the applied voltage. What is in the box?


Eric

 

a wheatstone bridge with an inverted side? Like this:

the 12V source represents your applied voltage, and points C & D represent your output leads. Potential difference between C & D is 4V (1/3 applied voltage in this case).

 

I agree in principal but don't the resistors have to hold the ratio X:3X to satisfy the 1/4 voltage requirement?

 

I agree in principal but don't the resistors have to hold the ratio X:3X to satisfy the 1/4 voltage requirement?

The values can be changed to make it hold a 1/4 voltage when voltage is applied from opposite corners, but when it is applied on the same side, it no longer works. So I proved myself wrong. I'll think about more tomorrow. Good night.

 

Here's what I think it is:

 

Here's what I think it is:

View attachment 91905

Nice! And you even made it look like a box!

 

Free hint: It can be done with just 5 resistors

 

You have a black box with four leads coming out of it. You apply a voltage (ac or dc) to any two adjacent leads. The two remaining leads output precisely 1/4 of the applied voltage. What is in the box?

If the four leads are in a row, does the outside pair constitute an adjacent pair as if the four leads were in a box?
Or does four-in-a-row intentionally have one fewer possible connection?

ak

 

Version 02:

 

Version 02:
View attachment 91932

So, I assume "Blocco a Spirale" translates to, "Master of Voltage Dividers"

PS: I know it is a "spiral notepad" but I like my translation better for today.

 

So, I assume "Blocco a Spirale" translates to, "Master of Voltage Dividers"

PS: I know it is a "spiral notepad" but I like my translation better for today.

I'll settle for "Master of guesswork that just happened to lead to a quick solution but may not be so lucky next time"

 

Here ya go.

 

Here ya go.

Well, that makes sense