Inductor-Resistor Series Circuit (Connection to Supply)

Chapter 8.3 Inductor-Resistor Series Circuit (Connection to Supply)

Fundamental Electrical and Electronic Principles Third Edition Book
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Fundamental Electrical and Electronic Principles Third Edition Book

  • 256Fundamental Electrical and Electronic Principles After one time constant the discharge current will have fallen to 0.368 I 0 II03062503300454 50 368454067 26ERiivRampAA1111...iRvR263267 2600084 voltV 111111..Ans 8.3 Inductor-Resistor Series Circuit (Connection to Supply) Consider the circuit of Fig. 8.11. At some time t 0, the switch is moved from position ‘ A ’ to position ‘ B ’ . The connection to the supply is now complete, and current will start to fl ow, increasing towards its fi nal R‘B’‘A’ERLiVRVL Fig. 8.11 steady value. However, whilst the current is changing it will induce a back-emf across the inductor, of e volt. From electromagnetic induction theory we know that this induced emf will have a value given by: eLitdd volt Being a simple series circuit, Kirchhoff ’ s voltage law will apply, such that the sum of the p.d.s equals the applied emf. Also, since we are considering a perfect inductor (the resistor shown may be considered as the coil ’ s resistance), the p.d. across the inductor will be exactly equal but opposite in polarity to the induced emf. Therefore, ddvolthence, voltor, ddveLitEvvEiRLiLRLttvolt ............... [ ]1 Comparing this equation with that for the C-R circuit, it may be seen that they are both of the same form. Using the analogy technique, we