Focal lengths in the fourth lab (the one with the lenses), you graphed the inverse of the image distance (1/d,) against the inverse of the object distance (1/do). how did you find the focal length of your lens from this graph? the thin lens equation

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?