Which statements correctly describe the properties of air? Select three options. Air has mass but no weight. Air pressure is created by the weight of the atmosphere pushing on Earth’s surface. Pressure is a measure of how tightly molecules are packed. Denser air is heavier than less dense air. Air is less dense at higher altitudes.

Electromagnetic induction. a coil of wire contains n turns and has an electrical resistance r. the radius of each turn is a. initially, inside the coil there exists a uniform magnetic field of magnitude b0 parallel to the axis of the coil. the magnetic field is then reduced slowly. the current induced in the coil is i. how long does it take for the magnitude of the uniform field to drop to zero?