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AB is 1 meter long uniform wire of 10 Om...

AB is `1` meter long uniform wire of `10 Omega` resistance. Other data are shown in the diagram. Calculate (i) potential gradient along `AB` (ii) length `AO` when galvanometer shown deflection

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(i) Total resistance of potentiometer wire circuit
`R = 15 +10= 25 Omega , epsilon = 2 V, L=100 cm`
Current in the potentiometer wire is
`I = epsilon/R = 2/25 = 0.08A`
potential difference across wire AB,
`V= 1 xx` resistance of wire AB
`:. V = 0.08 xx 10 = 0.8 V`
Potential gradient,
`K = V/L = 0.8/100 = 0.008 V cm^(-1)`
(ii) Resistance of secondary circuit
`R' = 1.2 + 0.3 = 1.5 Omega, emf q' = 1.5V`
Current in secondary circuit,
`I' = (epsilon')/(R') = 1.5/1.5 = 1A`
The current in `0.3 Omega` is I' ( = 1A)
Pot. diff. between points A and O is
V' = Pot. diff. across `0.3 Omega` resistance
`= I' xx 0.3 = 1 xx 0.3 = 0.3V`
length AO `= (V')/(K) = 0.3V/K = (0.3 V)/(0.008V cm^(-1))`
`= 37.5 cm`
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