# Homework help

#### Todd Piskura

Joined Oct 14, 2011
4
A device is rated to operate at a voltage of 24v. It has a protection circuit consisting of (4) 25 amp fuses. Question: Discuss whether these fuses are connected in series or parallel. Question: What is the maximum power of the device? Question: If this device was re-designed to operate at 12v, while still providing the same power, quantitatively assess the new demands of the circuit.

#### Georacer

Joined Nov 25, 2009
5,182
The Homework Help section asks that you post up the work you have done so far, so we can see it and find where you went wrong, or suggest better approaches. We will not do all your work for you.

Thank you.

#### Todd Piskura

Joined Oct 14, 2011
4
My thoughts are that the fuses must be in parallel with respective loads, to have 4 fuses in series really doesn't make any sense. The max power should be 25a times 24 volts or 600 watts. To change the circuit to 12v and keep the same power you would need 50 amps and 50 amp fuses. What do you think?

#### JoeJester

Joined Apr 26, 2005
4,390
My thoughts are that the fuses must be in parallel with respective loads, to have 4 fuses in series really doesn't make any sense.

#### Todd Piskura

Joined Oct 14, 2011
4
Thanks Joe, I'm guessing that I was wrong after drawing it but why do they need 4 25a fuses in series, isn't 1 good enough.

#### JoeJester

Joined Apr 26, 2005
4,390
It appears the homework assignment doesn't necessarily need to make sense. It is an exercise of the mind with the what if's.

With four series fuses, the device can only be 24V * 25A or 600W. With four parallel fuses, the device could be 24V * (4 * 25A) or 2400 W.

Now on the second part ... dropping it down to 12V ... The 600W load would require a minimum of two 25A fuses in parallel as the current demand would be 50A. The 2400 W would require 200 Ampere fuses or eight 25Ampere fuses in parallel.

If they wanted a more definitive answer, the "device" specifications would have been clearer.

#### Todd Piskura

Joined Oct 14, 2011
4
Thanks Joe, I wasn't really understanding what was going on, the last posts really helps me to understand what he is looking for. I appreciated the help.

#### #12

Joined Nov 30, 2010
18,217
Figuring out what the instructor is looking for has always been a problem. That's one of the reasons that weekly quizzes and homework assignments are given. You get to practice figuring out the instructor before the tests that really make a difference in your grade.