(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

You are given a device with which to operate with an input resistance of 50 W. The device requires 9 V to operate. However, the only available power supply is a 12 V source.

Part A:Using only resistors, design an interface circuit to lower the 12 V to 9 V for operating the device.

Part B:If the power supply has a 10 W internal resistance, what will be the voltage of the load?

Part C:How would you adjust it so that you get a 9 V voltage again?

2. Relevant equations

[tex]V_{out} = \frac{R_{2}}{R_{1} + R_{2}} \cdot V_{in}[/tex]

3. The attempt at a solution

ForPart A, can't I simply use a voltage divider to drop the 12V to 9V? If I set ,

[tex]R_{1} = 1 \Omega[/tex]

and,

[tex]R_{2} = 3 \Omega[/tex]

Then I should obtain a [tex]V_{out} = 9V[/tex].

Part B & Cis where I start to get a little confused.

ForPart B, if the power supply has 10 W internal resistance and it says in the question that the device has an input resistance of 50 W does that mean the other 40 W will be on the load?

Part Cis hooked intoPart Bso until I fully understand that, I don't think I have a shot at answeringPart C.

Any ideas/comments/suggestions?

Thanks again!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Interface circuit for a device with internal resistance

**Physics Forums | Science Articles, Homework Help, Discussion**