In the circuit of figure 3 9 write kvl equation

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! in the circuit of Figure 3-9. Write KVL equation around the right loop: V ! + ( 3 V ) + ( 4 V ) ( 5 V ) = 0 Solve for ࠵? ! and obtain: ࠵? ! = 2 ࠵? T YPICAL PROBLEMS FOR SELF - ASSESSMENT Problem 1 Figure 9 In the circuit shown on this diagram, the voltage across the shaded element is not given. The unknown voltage Z equals: A. 8 ࠵? B. 9 ࠵? C. 22 ࠵? D. + 44 ࠵? E. Not enough information. Book Page 27
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EE for the 21 st century Review the basics 1-1-2 Kirchhoff’s law for electric voltages © 2015 Alexander Ganago Page 10 of 11 Last printed 2015-07-24 6:16 PM File: 2015 1-1-2 KVL.docx Problem 2 Figure 10. The unknown voltage X equals: A. 16 ࠵? B. 8 ࠵? C. + 16 ࠵? D. + 8 ࠵? E. None of the above answers is within 10% of the correct answer. C ON Q UESTS = C ONCEPTUAL QUESTIONS 1 Can you explain how the following statement relates to the universal principle of conservation of energy? When two or more circuit elements are connected in parallel, the same voltage is applied to each of them. 2 An alkaline battery is built of individual, elementary cells, each of which provides about 1.5 V between its terminals. How would you connect 6 such cells to obtain one 9-V battery: in series, in parallel, or combining series and parallel connections? What advantage can you get in building one 9-V battery out of 12 elementary cells? How would you connect the individual cells in order to get this advantage? Book Page 28
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EE for the 21 st century Review the basics 1-1-2 Kirchhoff’s law for electric voltages © 2015 Alexander Ganago Page 11 of 11 Last printed 2015-07-24 6:16 PM File: 2015 1-1-2 KVL.docx S UMMARY ü The electric voltage, or potential difference, between points A and B equals by definition to the amount of work needed to move a unit positive charge between these points. ü The unit of voltage is volt, related to the units of electric charge and work in the following way: 1 ࠵?࠵?࠵?࠵? × 1 ࠵?࠵?࠵?࠵?࠵?࠵?࠵? = 1 ࠵?࠵?࠵?࠵?࠵? [Equation 1] ü Kirchhoff’s law for voltages (KVL): in any electric circuit, the total change of voltages around any closed loop equals zero. Mathematically, around any closed loop in a circuit, the algebraic sum of voltages equals zero. An alternative formulation is: The sum of all voltage rises equals the sum of all voltage drops around any closed loop in a circuit. ü KVL equation is written for the sum of voltages around a closed path in the circuit; the algebraic sign of the voltage across each circuit element is the same as the sign of the terminal of this element, which you encounter first. ü When writing a KVL equation, which includes an unknown voltage, choose its reference polarity to your convenience (or as given in the assignment); do not fret about the actual polarity of this voltage because you will obtain it after you have solved the equations.
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  • Fall '07
  • Ganago
  • Electric charge, Alexander Ganago

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