Fundamentals of Electrical Circuits C H A P T E R 2 Fundamentals of Electrical Circuits

Figure 2.4 (a) Automotive circuits

Figure 2.4 (b) Equivalent electrical circuit batt (b) + – I head tail start fan locks dash

Figure 2.8 (a) Electrical vehicle battery pack DC-AC converter (electric drive) 12 V AC motor (a) V batt1 batt2 battn

Figure 2.8 (b) Illustration of KVL Power converter and motor v batt1 + – drive batt2 batt3 batt31 (b)

Figure 2.10 Various representations of an electrical system Headlight Car battery + – R i v Source Load (a) Conceptual representation Power flow (b) Symbolic (circuit) (c) Physical _ V S

Figure 2.18 Volt-ampere characteristic of a tungsten light bulb 0.1 0.2 0.3 0.5 0.4 – 20 30 40 50 60 10 i (amps) v (volts) Variable voltage source Current meter +

Figure 2.20 The resistance element v + – A l 1/ i-v characteristic Circuit symbol Physical resistors with resistance R. Typical materials are carbon, metal film. R =

Figure 2.22 Resistor color code b 4 3 2 1 Color bands black brown red orange yellow green 5 blue violet gray white silver gold 6 7 8 9 10% 5% Resistor value = ( ) 10 ; = % tolerance in actual value

Figure 2.30 The current flows through each of 1.5 V + _ R v – i flows through each of the four series elements. Thus, by KVL, 1.5 = 1 2 3 R 1 R 2 R 3 n N EQ series resistors are equivalent to a single resistor equal to the sum of the individual resistances.

Figure 2.32 Parallel circuits + – v KCL applied at this node The voltage appears across each parallel element; by KCL, i S = 1 2 3 N resistors in parallel are equivalent to a single equivalent resistor with resistance equal to the inverse of the sum of the inverse resistances. R EQ n

Figure 2.36 Wheatstone bridge circuits 1 v S a + _ (a) x b d (b)

Figure 2.37 A force-measuring instrument 1 v S 4 b a d c + – i h w Beam cross section , bonded to bottom surface F

Figure 2.38 Practical voltage source + _ v – Practical voltage source = lim max The maximum (short circuit) current which can be supplied by a practical voltage source is

Figure 2.39 Practical current source + – v r A model for practical current sources consists of an ideal source in parallel with an internal resistance. Maximum output voltage for practical current source with open-circuit load: max =

Figure 2.41 Measurement of current + _ v S A series circuit A Symbol for ideal ammeter Circuit for the measurement of the current i

Figure 2.42 Measurement of voltage 1 + _ v S A series circuit V Ideal voltmeter Circuit for the measurement of the voltage i –

Figure 2.43 Models for practical ammeter and voltmeter

Figure 2.44 Measurement of power 1 + _ Internal wattmeter connections 2 v – S i Measurement of the power dissipated in the resistor : P = W V A

Figure 2.45 Definition of a branch m A Practical ammeter Ideal resistor R v A battery A branch Branch voltage current + – b i Examples of circuit branches

Figure 2.47 Definition of a node Examples of nodes in practical circuits Node a Node b v S i Node c Node

Figure 2.48 Definition of a loop v S R 1-loop circuit 3-loop circuit (How many nodes in this circuit?) Note how two different loops in the same circuit may in- clude some of the same ele- ments or branches. i 1 2

Figure 2.49 Definition of a mesh 3 v S Mesh 1 4 i Mesh 3 5 2 + _ How many loops can you identify in this four-mesh circuit? (Answer: 14)