This ratio given in ohms per volt or v is known as

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Unformatted text preview: o of the total resistance (Rn + Rm ) to the full-scale voltage Vfs is constant and equal to 1/Ifs for the four ranges. This ratio (given in ohms per volt, or /V) is known as the sensitivity of the voltmeter. The larger the sensitivity, the better the voltmeter. PRACTICE PROBLEM 2.17 Following the ammeter setup of Fig. 2.61, design an ammeter for the following multiple ranges: (a) 0 –1 A (b) 0 –100 mA (c) 0 –10 mA Take the full-scale meter current as Im = 1 mA and the internal resistance of the ammeter as Rm = 50 . Answer: Shunt resistors: 0.05 , 0.505 , 5.556 . 2.9 SUMMARY 1. A resistor is a passive element in which the voltage v across it is directly proportional to the current i through it. That is, a resistor is a device that obeys Ohm’s law, v = iR where R is the resistance of the resistor. 2. A short circuit is a resistor (a perfectly conducting wire) with zero resistance (R = 0). An open circuit is a resistor with infinite resistance (R = ∞). 3. The conductance G of a resistor is the reciprocal of its resistance: G= 1 R 4. A branch is a single two-terminal element in an electric circuit. A node is the point of connection between two or more branches. A loop is a closed path in a circuit. The number of branches b, the number of nodes n, and the number of independent loops l in a network are related as | v v b =l+n−1 | e-Text Main Menu | Textbook Table of Contents | Problem Solving Workbook Contents CHAPTER 2 Basic Laws 5. Kirchhoff ’s current law (KCL) states that the currents at any node algebraically sum to zero. In other words, the sum of the currents entering a node equals the sum of currents leaving the node. 6. Kirchhoff ’s voltage law (KVL) states that the voltages around a closed path algebraically sum to zero. In other words, the sum of voltage rises equals the sum of voltage drops. 7. Two elements are in series when they are connected sequentially, end to end. When elements are in series, the same current flows through them (i1 = i2 ). They a...
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This note was uploaded on 07/16/2012 for the course KA KA 2000 taught by Professor Bkav during the Spring '12 term at Cambridge.

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