A multirange voltmeter can be constructed by using a galvanometer circuit as shown in the figure. We want to construct a voltmeter that can measure 2V, 20V and 200V using a galvanometer of resistance 10Ω and that produces maximum deflection for current of 1 mA. Find the value of R1, R2 and R3 that have to be used.
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the value of R1, R2 and R3 that have to be used will be found by the following process
given:
G=10Ω
Ig=1mA=10¬³AV=2R1=V/Ig − G=2/10¬³ − 10=1990Ω=2kΩ
v=20v,(R1+R2)=20¬³ - 10
20,000−10∘≈20kΩ
v=200v,R1+R2+R3= 200/10¬³ - 10
≈200KΩ
R1=2kΩ,
R2=20kΩR3=200−20 =180kΩ
Answer is 180KΩ
the value of R1, R2 and R3 that have to be used will be found by the following process
given:
G=10Ω
Ig=1mA=10¬³AV=2R1=V/Ig − G=2/10¬³ − 10=1990Ω=2kΩ
v=20v,(R1+R2)=20¬³ - 10
20,000−10∘≈20kΩ
v=200v,R1+R2+R3= 200/10¬³ - 10
≈200KΩ
R1=2kΩ,
R2=20kΩR3=200−20 =180kΩ
Answer is 180KΩ
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