15.04.2014 Views

Introduction to SAT II Physics - FreeExamPapers

Introduction to SAT II Physics - FreeExamPapers

Introduction to SAT II Physics - FreeExamPapers

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Consider again the circuit whose <strong>to</strong>tal resistance we have calculated. What is the current<br />

through each resis<strong>to</strong>r? What is the power dissipated in each resis<strong>to</strong>r?<br />

WHAT IS THE CURRENT RUNNING THROUGH EACH RESISTOR?<br />

We know that resis<strong>to</strong>rs in series do not affect the current, so the current through<br />

is the<br />

same as the <strong>to</strong>tal current running through the circuit. Knowing the <strong>to</strong>tal resistance of the<br />

circuit and the voltage drop through the circuit, we can calculate the circuit’s <strong>to</strong>tal current<br />

by means of Ohm’s Law:<br />

Therefore, the current through is 3 A.<br />

But be careful before you calculate the current through and : the voltage drop<br />

across these resis<strong>to</strong>rs is not the <strong>to</strong>tal voltage drop of 30 V. The sum of the voltage drops<br />

across<br />

and the two resis<strong>to</strong>rs in parallel is 30 V, so the voltage drop across just the<br />

resis<strong>to</strong>rs in parallel is less than 30 V.<br />

If we treat the resis<strong>to</strong>rs in parallel as a single equivalent resis<strong>to</strong>r of 6<br />

the voltage drop across the resis<strong>to</strong>rs by means of Ohm’s Law:<br />

, we can calculate<br />

Now, recalling that current is divided unevenly between the branches of a set of resis<strong>to</strong>rs<br />

in parallel, we can calculate the current through and in the familiar way:<br />

WHAT IS THE POWER DISSIPATED ACROSS EACH RESISTOR?<br />

229

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!