Ch 26 Circuits_2009

Ch 26 Circuits_2009 - Go over mid term first Direct Current...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
Direct Current Circuits Chapter 26 In this chapter we discuss only direct currents used in such circuits as flashlights and automobile circuits . Household appliances use alternating currents and are not discussed in this section. Go over mid term first
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
One of the most common direct current circuit elements [and alternating current] is the resistor.
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Resistors can occur in combinations with other resistors. We will study resistors that occur in series and parallel circuits as shown in the diagrams to the right. The question is what then will be the equivalent resistance of resistors in parallel and series combinations ? That is, if you replace any of the network circuits to the right by a single resistor, how would we determine that single resistance? Such that: I V R ab eq =
Background image of page 4
Resistors in Series If the resistors are in series the current must be the same through all of them ( moving charge is not used up as it passes through a circuit ). Applying Ohm’s law we have for the series circuit: V ax = IR 1 ; V xy = IR 2 ; V yb = IR 3 Furthermore, since potential is related to work and work adds, thus electrical potential adds due to each resistor, which takes Joule energy away from the electrons.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The potential difference across each resistor in general will not be the same. Nonetheless, potential like work adds hence: V ab = V ax + V xy + V yb = IR 1 + IR 2 + IR 3 V ab = I(R 1 + R 2 + R 3 ) Thus And so 3 2 1 R R R I V R ab eq + + = = Simply put resistors in series add.
Background image of page 6
Resistors in Parallel Like water through a pinched versus an open hose, resistors in parallel can have different amounts of flow of electrons (current) through them. However, just like “ water pressure ”, resistors like hoses connected in parallel will have the same pressure ; that is the same electric potential or voltage drop across each circuit element or resistor R 1 , R 2 and R 3 .
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 2 R V I ab = 1 1 R V I ab = 3 3 R V I ab = The total current in is simply the sum of the currents through each resistor. + + = + + = + + = 3 2 1 3 2 1 3 2 1 1 1 1 R R R V R V R V R V I I I I ab ab ab ab That is: eq ab R R R R V I 1 1 1 1 3 2 1 = + + =
Background image of page 8
And so we see for resistors in parallel the equivalent resistance is given by: + + + + = n eq R R R R R 1 ... 1 1 1 1 3 2 1 The equivalent resistance is always less than any individual resistance.
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Compute the equivalent resistance of the network from the figure below and find the current in each resistor:
Background image of page 10
the 6 Ohm and the 3 Ohm resistors in parallel. Hence we use the parallel resistor formula. + + + + = n eq R R R R R 1 ... 1
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 10/05/2011 for the course PHYS 4B taught by Professor W.christensen during the Summer '09 term at Irvine Valley College.

Page1 / 46

Ch 26 Circuits_2009 - Go over mid term first Direct Current...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online