What are london dispersion forces?
The exam board that I teach has just switch from using the term instantaneous dipole - induced dipoles to using London forces, and the switch does not make sense.
In a non-polar molecule the electrons are constantly moving around, at some point by random, they will mostly be towards one end of a molecule creating an instantaneous dipole. This will lead to one end of the molecule being a bit positive and the other end being a bit negative. The sudden occurrence of this dipole will trigger an induced dipole in a neighboring molecule. The positive and negative dipoles will be attracted to each other and this is a London force.