In the figure below, a voltmeter of resistance R V = 400 , and an ammeter of res
ID: 2144518 • Letter: I
Question
In the figure below, a voltmeter of resistance RV = 400 , and an ammeter of resistance RA = 3.00 are being used to measure a resistance R in a circuit that also contains a resistance R0 = 100 and an ideal battery of emf = 9.0 V. Resistance R is given by R = V/i, where V is the voltmeter reading and i is the current in resistance R. However, the ammeter reading is not i, but rather i', which is i plus the current through the voltmeter. Thus, the ratio of the two meter readings is not R, but only an apparent resistance R' = V/i'.
In the figure below, a voltmeter of resistance RV = 400 , and an ammeter of resistance RA = 3.00 are being used to measure a resistance R in a circuit that also contains a resistance R0 = 100 and an ideal battery of emf = 9.0 V. Resistance R is given by R = V/i, where V is the voltmeter reading and i is the current in resistance R. However, the ammeter reading is not i, but rather i', which is i plus the current through the voltmeter. Thus, the ratio of the two meter readings is not R, but only an apparent resistance R' = V/i'.Explanation / Answer
a)
equivalent resistance
Req =(R||RV)+Ro+RA
Req =(R*RV/R+RV) +Ro+RA
Req =(400*85/400+85) +100+3
Req =173.1 ohms
I=E/Req =9/173.1
I =0.052 A
b)
V=E -I(RA+R0)
V=9-0.052(3+100)
V=3.645 V
c)
R' =V/I =3.645/0.052
R'=70.1 ohms