The rheostat is made of nickel wire with a resistivity of 0.4 • 10 ^ -6 Ohm • m, a length of 15 m

| June 2, 2021 | education

The rheostat is made of nickel wire with a resistivity of 0.4 • 10 ^ -6 Ohm • m, a length of 15 m and a cross-sectional area of 1 mm2. Find the current in the circuit if the voltage at the terminals of the rheostat is 18 V.

According to Ohm’s Law:
I = U / R, where I is the current in the wire, U is the voltage at the rheostat terminals (U = 18 V), R is the resistance of the nickel wire.
R = ρ * l / S, ρ is the resistivity of the nickel wire (ρ = 0.4 * 10 ^ -6 Ohm * m), l is the length of the nickel wire (l = 15 m), S is the cross-sectional area of the nickel wire (S = 1 mm ^ 2 = 1 * 10 ^ -6 m).
Let’s calculate the current strength:
I = U * R = U / (ρ * l / S) = U * S / (ρ * l) = 18 * (1 * 10 ^ -6) / ((0.4 * 10 ^ -6) * 15 ) = 3 A.
Answer: The current strength is 3 A.



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