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Question
A potentiometer wire has a length of 4 m and resistance of 20 Ω. It is connected in series with resistance of 2980 Ω and a cell of emf 4 V. Calculate the potential along the wire.
Solution
Given data:
l = 4m of R = 20Ω
In series with R’ = 2980Ω
E = 4 V
Since 20 is in series with 2980
Reff = 20 + 2980 = 3000
current I = `"V"/"R"_"eff" = 4/3000 = 1.3 xx 10^-3 "A"`
I = `1.3 xx 10^-3`A
Potential along the wire of 4 m length is,
`"V"/"l" - "IR"/"l" = (1.3 xx 10^-3 xx 20)/4`
`= (26 xx 10^-3)/4`
= 6.5 × 10-3 Vm-1
`"V"/"l" = 6.5 xx 10^-2 "Vm"^-1`
Potential = `0.65 xx 10^-2 "Vm"^-1`
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