![]() |
| Powered by phpBay Pro |

Electric Circuits questions please!?
1. a)The potentiometer extends between positions 1.9 cm and 54.6 cm on the scale. The voltage read by the DMM is 1.000 V and the current read the by DMM is 42mA. What is the resistance per unit length of the nichrome wire? (Does the DMM affect the resistance measurement?)
b)The accuracy of the multimeter is cited as ±0.7% ±1 digit on the voltage range and ±1% ±1 digit for the 300 mA range. What are the uncertainties of the voltage and current readings and the resultant uncertainty of the resistance of the wire?
2. a)Show that I(t) = (I_0)(e^(-t/RC)) solves the differential equation for the current through a discharging capacitor if I_0 = V_0/R, and t=0 is the time the discharging starts. Hint: Use Ohm's law, Kirchoff's laws and the identity de^(at)/dt = ae^(at)
b) Find the charge and voltage on the capacitor as a function of time.
1 a) Resistance per unit length = [1.000/(42*10^-3)]/(54.6 - 1.9) = 0.45 ohm cm^-1 DMM internal resistance is very high so it does not affect the resistance measurement.
b) Voltage as measured in A = 1.000 +/-0.007 and current = 42 +/-0.42
Corresponding uncertainty in resistance = 0.007+0.01 = 0.017 times resistance. So Resistance of the wire = 1000/42 = 23.82 +/-(23.82*0.017) = 23.8+/-0.4
2 a) By Kirchhoff laws we have
Q/C + IR = V or dQ/dt + (RC)*dI/dt = 0 or
dI/dt + (1/RC)*I = 0 or
dI/I = - dt/(RC) or ln I = -t/(RC) +C, when t = 0 I = V/R = Io say, this gives
I = Io*e^-[t/(RC)]
b) Vc = V - IR = IoR - IoR*e^-[t/(RC)] = V[1-e^-{t/(RC)}]
Q = CV[1-e^-{t/(RC)}] = Qo[1-e^-{t/(RC)}] where Qo is the maximum charge that capacitance can store for potential difference = V
![]() |
![]() KEITHLEY 2001 Digital MULTIMETER 7 1 2 DIGIT DMM US $2,100.00
|
![]() Keithley 2001 High Performance 7 1 2 Digit DMM w 8k Memory US $2,000.00
|
![]() KEITHLEY 2001 Digital MULTIMETER 7 1 2 DIGIT DMM US $1,850.00
|
![]() Agilent HP 34401A Digital Multimter 65 Digit DMM GPIB Calibrated 05 Nice US $699.99
|
![]() Agilent 34401A Digital Multimeter 65 Digit 4 US $699.95
|
![]() Agilent 34401A Digital Multimeter 65 Digit 5 US $699.95
|
![]() HP 34401A Digital Multimeter 65 Digit 6 US $699.95
|
![]() HP 34401A Digital Multimeter 65 Digit 7 US $699.95
|
![]() Agilent 34401A Digital Multimeter 65 Digit 1 US $699.95
|
![]() Instek GDM 8255A 5 1 2 digit Digital Multimeter 199000 counts US $639.00
|
![]() Agilent HP 34401A 65 digit Digital Multimeter US $595.00
|
![]() BK PRECISION 2831D 4 1 2 DIGIT TRUE RMS DIGITAL MULTIMETER US $575.00
|
![]() KEITHLEY 2015 THD Total Harmonic Distortion 6 1 2 Digit DMM US $550.00
|
![]() Instek GDM 8251A 5 1 2 digit Digital Multimeter 120000 counts US $549.00
|
![]() HP Agilent 3478A 55 Digit DMM with GPIB US $500.00
|
![]() KEITHLEY 2000 Digital MULTIMETER 6 1 2 DIGIT DMM US $500.00
|
![]() HP Agilent 3478A 55 digit DMM with HP IB interface US $495.00
|
![]() NEW 5 1 2 DIGIT DIGITAL BENCH TOP MULTIMETER DMMUSB US $487.00
|
![]() FLUKE 8800A DIGITAL MULTIMETER 55 DIGIT 200MV 1200VAC US $420.00 |
![]() HP 3457A 65 75 Digit Bench Top System Digital Multimeter Rack Mountable US $417.99
|
![]() Fluke 8842A 55 Digit Digital MultiMeter US $400.00
|
![]() Keithley 195A Opt 1950 AC Amps DMM 5 1 2 Digit IEEE 488 US $349.95
|
![]() FLUKE 8842A DIGITAL MULTIMETER 55 DIGIT With IEEE 05 09 US $340.00
|
![]() Keithley 196 65 digit system DMM US $329.00
|
![]() Agilent Hewlett Packard 3478A Digital Multimeter DMM 55 Digit Warranty US $325.00
|
![]() Keithley 196 System Digital Multimeter 65 Digit DMM US $325.00
|
![]() HP 3456A Digital Multimeter 65 digit US $325.00
|
![]() KEITHLEY 192 DIGIT PROGRAMMABLE DMM W IEEE 488 US $320.00
|
![]() BK Precision 5492 5 1 2 digit Dual Display Digital Multimeter US $320.00
|
![]() Protek B845 4 1 2 Digit Bench DMM Digital Multimeter US $276.00
|
![]() Keithley 195A Digital Multimeter 55 DIGIT DMM US $225.00
|
![]() HP 3478A Digital Multimeter 5 1 2 Digit No Probes US $219.99
|
![]() PROTEK 3 3 4 DIGIT 4000 COUNT TRUE RMS BENCH TOP DMM WITH RS 232 US $209.95
|
![]() HP AGILENT 34401A Digital Multimeter 6½ Digit US $200.00
|
![]() HP 3478A Digital Multimeter 55 Digit 1 US $199.95
|
![]() HP 3478A Digital Multimeter 55 Digit 2 US $199.95
|
![]() Data Precision 2480R Analogic Digit Digital Multimeter US $114.99
|
![]() HP 3478A Digital Multimeter DMM 5 1 2 Digit HP IB GPIB Benchtop 2 Wire 4 Wire US $112.99
|
| Powered by phpBay Pro |


US $6,295.00




















































































