The figure below shows a very fine current-carrying (L × w) = (4 cm × 1 cm) rectangular wire loop being levitated by a current-carrying wire h = 3 mm from its top edge. The combined mass of the wire loop and the battery driving the I2 = 0.5 A current through it (not pictured) is m = 0.23 g. What is the current through the straight wire, I1? 1 个

2) An iron atom has a mass of m = 9.273 × 10−26 kg, permanent magnetic dipole moment of M = 1.8 × 10−23 Am2 , and is approximately spherical with radius 1.4 × 10−10 m. Suppose that an iron atom is held in place so that its magnetic dipole moment is perpendicular to Earth’s magnetic field (B = 5.1×10−6 T). What is its angular acceleration when first released?