a)How large a parallel resistor R a mustbe placed in parallel with the D’Arsonva

Question

a)How large a parallel resistor Ra  mustbe placed in parallel with the D’Arsonval meter movement toextend its useful measuring range to 1A ? b)For the design completed in Prob. a determine themeasured current that flows when the D’Arsonval metermovement is connected to an energized circuit and it reads3mA . a)How large a parallel resistor Ra  mustbe placed in parallel with the D’Arsonval meter movement toextend its useful measuring range to 1A ? b)For the design completed in Prob. a determine themeasured current that flows when the D’Arsonval metermovement is connected to an energized circuit and it reads3mA . b)For the design completed in Prob. a determine themeasured current that flows when the D’Arsonval metermovement is connected to an energized circuit and it reads3mA .

Explanation / Answer

I assume that this question is with respect to the D"Arsonalmeter mentioned in the previous question. The resistance of the D'Arsonal metermovement   Rm = Vfs / Ifs Rm = 100m / 10m Rm = 10 Given Ifs = 10mA To convert to a range of I = 1A A resistance Rp is connected in parallel with themeter movement. Now the voltage across the meter will be equal to the voltageacross Rp as they are in parallel Vm = Vp ImRm = IpRp Rp = ImRm /Ip The current through Rp will be Ip = I - Im Rp = ImRm /(I-Im) Rp = (0.01)(10) / (1-0.01) Rp = 0.1 Thus to extend the measurement to 1A a resistance ofRp= 0.101 should be connected in parallel with themeter. b) When I = 3mA Current through the meter movement Rp = ImRm /(I-Im) 0.101 = Im (10) / (0.003 - Im) 0.000303 - 0.101Im = 10Im 0.000303 = 9.899Im Im = 0.0000306A
Im = 30.6A

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.