Determine the current strength in the section of the circuit consisting of a 20 M long constantan wire with a cross section of 1.2 mm (2), if the voltage at the ends of this section is 40 V.
Initial data: l (length of constantan wire) = 20 m; S (wire section) = 1.2 mm2; U (voltage at the ends of the constantan wire section) = 40 V.
Constants: ρ (resistivity constantan) = 0.5 Ohm * mm2 / m.
1) Resistance of the circuit section: R = ρ * l / S = 0.5 * 20 / 1.2 = 8.33 Ohm.
2) Current in the circuit section: I = U / R = 40 / 8.33 = 4.8 A.
Answer: The current in the constantan wire section of the circuit is 4.8 A.
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