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प्रश्न
A potentiometer wire has a length of 4 m and a resistance of 5 Ω. What resistance should be connected in series with a potentiometer wire and a cell of e.m.f. 2 V having internal resistance 1 Ω to get a potential gradient of 10-3 V/cm ?
उत्तर
Given:
L = 4m
R = 5Ω
E = 2V
Internal resistance of cell,
r = 1Ω
K = 10-3 V/cm
K = 10-3 /10-2
K = 0.1 V/m
To find:
RE = ?
Formulae:
K = IR/L
I = E/(R + r + RE)
Solution:
Since,
I = E/(R + r + RE)
∴ K = IR/L
K = ER/(R + r + RE)L
0.1 = (2 × 5)/(5 + 1 + RE) × 4
0.1 × 4 × (6 + RE) = 10
6 + RE = 25
∴ RE = 19Ω
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