C calculate the percent error introduced by the meter

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Unformatted text preview: R2 (a) 1 kΩ 5 kΩ 2 mA + vo − 4 kΩ Figure 2.122 Voltmeter 2.63 (b) Figure 2.120 2.61 For Prob. 2.60. (a) Find the current i in the circuit of Fig. 2.121(a). (b) An ammeter with an internal resistance of 1 is inserted in the network to measure i as shown in Fig. 2.121(b). What is i ? (c) Calculate the percent error introduced by the meter as An ammeter model consists of an ideal ammeter in series with a 20- resistor. It is connected with a current source and an unknown resistor Rx as shown in Fig. 2.123. The ammeter reading is noted. When a potentiometer R is added and adjusted until the ammeter reading drops to one half its previous reading, then R = 65 . What is the value of Rx ? Ammeter model I Rx 60 Ω Figure 2.123 2.64 v v (a) | | R 16 Ω 40 Ω V For Prob. 2.62. A 4V + − 100 kΩ 20 Ω i−i × 100% i i 60 Ω (b) (d) Find the percent error if the internal resistance were 36 k . 5 kΩ Ammeter 4V + − v o − vo × 100% vo 2 mA 71 e-Text Main Menu | Textbook Table of Contents | For Prob. 2.63. The circuit in Fig. 2.124 is to control the speed of a motor such that the motor draws currents 5 A, 3 A, Problem Solving Workbook Contents 72 PART 1 DC Circuits and 1 A when the switch is at high, medium, and low positions, respectively. The motor can be modeled as a load resistance of 20 m . Determine the series dropping resistances R1 , R2 , and R3 . 2.65 An ohmmeter is constructed with a 2-V battery and 0.1-mA (full-scale) meter with 100- internal resistance. (a) Calculate the resistance of the (variable) resistor required to be in series with the meter and the battery. (b) Determine the unknown resistance across the terminals of the ohmmeter that will cause the meter to deflect half scale. 2.69 An electric pencil sharpener rated 240 mW, 6 V is connected to a 9-V battery as shown in Fig. 2.126. Calculate the value of the series-dropping resistor Rx needed to power the sharpener. Low R1 10-A, 0.01-Ω fuse Medium High R2 6V R3 Motor Figure 2.124 For Prob. 2.64...
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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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