Задача 30986.

Solenoid length l = 1 m, diameter D = 10 cm. A wire with diameter d = 1 mm is tightly wound around the solenoid. How much current must be passed through the solenoid so that the energy of its magnetic field is equal to the energy of the Earth´s magnetic field contained in a room measuring 8*4*2.5 m^3? Find the ratio of the volumetric energy densities of the magnetic field of the solenoid and the Earth. Take the Earth´s magnetic field strength to be 40 A/m.

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