The Math for Ohms Law along in DC Circuits Chapter 11 Sections 1 and 2 The Math for Ohms Law along in DC Circuits

Ohm’s Law Math in Action Resistance in Series and Parallel Circuits Read section to answer the following: What do current limiting resistors do as part of an LED display board How does Kirchhoff’s Voltage Law relate to this Resistance in Series and Parallel Circuits First Step Calculating Series resistance. See Figure 11-1 on page 221 If the circuit has more than one resistor they are identified by a subscript on R and/or by values (if known) For (a) RT = R , (b) RT = R1 + R2 (c) RT = R1 + R2 + R3 For (c) RT = R1 + R2 + R3 (d) RT = R1 + R2 + R3 + R4 Do Examples 11-1, 11-2, & 11-3

Ohm’s Law Resistance in Series and Parallel Circuits Calculating Parallel resistance. See Figure 11-2 on page 222 If the circuit has more two or more resistors in parallel they are identified by a subscript on R and/or by values (if known) Conductance of a resistor = 1/R = G, R = 1/G In a parallel circuit the total conductance equals a sum of all the parallel components GT = G1 + G2 + G3 + …. + Gn RT = 1/GT Do Examples 11-4 and 11-5

Ohm’s Law Resistance in Series and Parallel Circuits Calculating Series-Parallel resistance. See Figure 11-3 on page 224 GT = G1 + G2 + G3 + …. + Gn RT = R1 + R2||R3 = R1 + RX , RX = 1/GX GX = G2 + G3 = 230uS  RX =4.34k ohms RT = R1 + 4.34 k ohms = 4.7 k ohms + 4.34 k ohms RT = 9.04 k ohms See Figure 11-5 on page 224 RT = R1 + R2||R3|| R4 = R1 + RX GX = 147uS + 100uS +303uS = 550uS RX = 1/GX = 1/550uS = 1.82k ohms

Ohm’s Law Resistance in Series and Parallel Circuits Calculating Series-Parallel resistance. See Figure 11-5 on page 225 RT = R1 + RX = 1.2k ohms + 1.82k ohms = 3.02k ohms