IB Coulomb's Law with Dielectrics

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A tutorial sheet of problems with dielectrics separating the charges is given below

  1. Two point charges, +2.0 nC and +2.0 nC are placed 5.0 cm apart in a vacuum. Draw the electric field around the charges and determine the electric force between the charges.
  2. The point charges in question 1 are now placed in a material of relative permittivity 4. Draw the electric field lines. Give a reason why the electric force between the charges increases/decreases/stays the same.
  3. A point charge -4.0 nC is at a height of 6.0 cm above a deep, still, freshwater lake. Draw the electric field lines in air and water. If the dielectric constant of water is 81 determine the electric force on the charge.[See p184 Electromagnetism by Lorrain and Corson, attraction, k(K-1)/(K+1)q2/(4d2), 9.75x10-6N]
  4. Two point charges +6.0 μC and -6.0 μC are placed 12.0 cm apart in a vacuum. An infinite rectangular slab of dielectric material of thickness 6.0 cm and relative permittivity 4 is placed with its surface 3.0 cm from each charge perpendicular to the line joining the charges. Draw the electric field lines and determine the electric force acting on each charge.

HSC Physics Atoms to Universe

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  1. Atoms emit discrete wavelengths of light. Explain why a heated iron bar changes colour as its temperature changes.
  2. The energy of an electron in the ground state of a hydrogen atom is -13.6 eV. (a) How can an electron have a negative energy? (b) What is the energy of an electron in the first excited state? (c) determine the value of the three longest wavelengths in the Balmer series for hydrogen.

  3. A proton moves at a constant speed of 0.90c. The proton moves once around the tube of a particle accelerator of circumference 20.0 km. (a) What are the momentum and the energy of the proton in the laboratory reference frame? (c) What is the distance travelled by the proton in its own reference frame?

  4. more to come