Fundamental Electrical and Electronic Principles, Third Edition

34 Fundamental Electrical and Electronic PrinciplesWorked Example 2.2QTwo resistors are connected in series across a battery of emf 12 V. If one of the resistors has a valueof 16 Ω and it dissipates a power of 4 W, then calculate (a) the circuit current, and (b) the value of theother resistor.ASince the only two pieces of data that are directly related to each other concernthe 16 Ω resistor and the power that it dissipates, then this information mustform the starting point for the solution of the problem. Using these data we candetermine either the current through or the p.d. across the 16 Ω resistor (and itis not important which of these is calculated first). To illustrate this point bothmethods will be demonstrated. The appropriate circuit diagram, which forms anintegral part of the solution, is shown in Fig. 2.3 .A B 16 Ω CV ABV BCIE12 VFig. 2.3E 12 V; R BC 16 Ω ; P BC 4 W(a)(b)I 2 R BC P BC wattI 2 RBC PBC4 0.2516so I 0.5 A AnsEtotal resistance, R ohm I12 24 Ω05 .R AB R R BC 24 16so R AB 8 Ω AnsAlternatively, the problem can be solved thus:(a)V2BC PBCwattRBCV2BC P BC R BC 4 16 64