Lab 1: Introduction to DC Circuits

Intro:

The purpose of this lab is to find the resistance of cables attached from a battery to a load. In the following figure. 

The cables are represented by a resistors, which we will call R_{Cable tot}.

Experiment:

To find the load resistance of a load supplied with 12V and consumes .044W we get

            R_Load=V^2/P=12^2/.144=1000 ohms

Data

R_Load = 998 ohms

V_load=11.00V

I_Batt = 11.45mA

R_{Cable tot} = 98 ohms

Analysis;

For a .8 Ahr the device will last

.8Ahr*.01145A=70.0 hours

The efficiency can be calculated by P_out/(P_out + P_Lost)

P_out = V^2/R=11^2/998

P_Lost = I^2V = (.01145)*98=.01284

P_out/(P_out + P_Lost)*100=90.41%

Given a resistance of AWG #30 of .345ohms/m the maximum distance is

            98ohms/(.345omhs/m)=284.0 m

An AWG# 28 that can keep a 20mA 5V signal is 1576ft long.

Sending a 48 volt signal at 10 amps that will deliver 36 volts to a sub 60ft  below needs a resistance of .02 ohms per feet. ohms.  AWG#22 is .0190 ohms per feet.