1) An oil drop of mass 4.92 x 10-15 kg is balanced between two large, horizontal parallel plates 4.3 cm wide, 7.2 cm long and 1.2 cm apart, maintained at a potential difference of 510.4 V. a) Draw a neat fully labelled diagram of the problem including forces, charges and distances.

b) How many elementary charges does the electron have?

c) Explain clearly to a Grade 9 student how Millikan was able to use an apparatus like this to determine that charge is always an integral multiple of an elementary charge.

Certain bacteria (such as aquaspirillum magnetotacticum) tend to swim toward the earth’s geographic north pole because they contain tiny particles, called magnetosomes, that are sensitive to a magnetic field. if a transmission line carrying 100 a is laid underwater, at what range of distances would the magnetic field from this line be great enough to interfere with the migration of these bacteria? (assume that a field less than 5% of the earth’s field would have little effect on the bacteria. take the earth’s field to be 5.0 * 10-5 t, and ignore the effects of the seawater.)