its for my final and I'm panicking

Ais useful when you need a simple machine to you separate two things. a. lever b. screw c. pulley d. wedge

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?

Which is the most accurate name for the covalent compound p2o3?