# A rheostat with a total resistance of 10.5 Ohm is made of 5m long nickelin wire

A rheostat with a total resistance of 10.5 Ohm is made of 5m long nickelin wire and a cross-sectional area of 0.2mm ^ 2, determine the specific resistance of nickelin.

To find the desired resistivity of nickelin, we use the formula to calculate the electrical resistance: R = ρ * l / S and ρ = R * S / l.
Values of variables: R – total resistance of the rheostat (R = 10.5 Ohm); S – cross-sectional area (S = 0.2 mm2); l is the length of the nickel wire (l = 5 m).
Let’s make a calculation: ρ = R * S / l = 10.5 * 0.2 / 5 = 0.42 Ohm * mm2 / m.
Answer: Nickelin, according to the calculation, has a specific electrical resistance of 0.42 Ohm * mm2 / m.

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