Lesson_3.4_Printable_PPT

Lesson_3.4_Printable_PPT - Direct Current Circuits...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon

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

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

Unformatted text preview: Direct Current Circuits Resistors in series Resistors can be combined suitably to produce a larger or a smaller resistor than the ones that are available. A series connection is an end to end connection as shown below. Three resistors, R 1 , R 2 and R 3 connected in series and connected to a source of potential V . V I I I I R 1 R 2 R 3 V 1 V 2 V 3 Three resistors, R 1 , R 2 and R 3 connected in series and connected to a source of potential V. V I I I I R 1 R 2 R 3 V 1 V 2 V 3 V is the total potential drop across the three resistors. If V 1 , V 2 and V 3 are the potential drops across R 1 , R 2 and R 3 respectively: V = V 1 + V 2 + V 3 But the current in each of the V I I I I R 1 R 2 R 3 V 1 V 2 V 3 V = V 1 + V 2 + V 3 resistors is the same, namely, I Dividing this equation by I we have: If R is the total resistance of the combination, then: R = R 1 + R 2 + R 3 3 1 2 V V V V I I I I = + + V I R = Example 1: What is the resistance of a series combination of four 2.0 ohm resistances? R = R 1 + R 2 + R 3 + R 4 = 2 + 2 + 2 + 2 = 8 Resistors in parallel V I I 1 I 2 I 3 R 1 R 2 R 3 A B When each resistor is connected across the same two points, we have a parallel connection . Three resistors R 1 , R 2 and R 3 are connected across two points A and B across which a potential difference V is maintained. This means that the potential difference across R 1 = potential difference across R 2 = potential difference across R 3 = V . I I 1 I 2 I 3 R 1 R 2 R 3 A B The total current I reaching A is split into I 1 which passes through R 1 , I 2 which passes through R 2 and I 3 which passes through R 3 . I = I 1 + I 2 + I 3 V Dividing this equation by V : 3 1 2 I I I I V V V V = + + 1 2 3 1 1 1 1 R R R R = + + If R is the total resistance: V I R 1 R 2 B A Resistors are connected in parallel when we need a resistance less than that are available. If two resistors R 1 and R 2 are in parallel, the equivalent resistance R is given by: 1 2 1 2 R R R R R = + 1 2 1 1 1 R R R = + 1 2 1 2 R R R R + = Example 2: A 1.0 , a 2.0 and a 3.0 are connected in parallel. What is the total resistance of the circuit? 1 2 3 1 1 1 1 R R R R = + + 1 1 1 1 2 3 = + + 11 6 = 6 11 R = 0.55 The total resistance is less than the smallest of the combined resistors. Example 3: The current in a loop circuit that has a resistance R 1 is 2.0 A. The current is reduced to 1.6 A when a resistor R 2 = 3.0 is added in series with R 1 . What is the value of R 1 ? If V is the potential difference across R 1 : V = 2R 1 R 1 2 A V R 1 1.6 A 3 V When a 3.0 is connected in series with R 1 , the total resistance is: R 1 + 3 The current now is: I = 1.6 A The voltage V remains the same....
View Full Document

This note was uploaded on 05/01/2011 for the course PHY 2049 taught by Professor George during the Spring '11 term at Edison State College.

Page1 / 45

Lesson_3.4_Printable_PPT - Direct Current Circuits...

This preview shows document pages 1 - 10. Sign up to view the full document.

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