Video of the lecture.

Showed that under a mild hypothesis on a differential 1-form w we have d(dw)=0. Gave an example which used this equation. Then quickly covered the basics on differential 3-forms, and their integration, and the total derivative of a 2-form. The treatment was such that it equally applies to differential k-forms (though the 1-dimensional notion of "length", and the 2-dimensional notion of "area", and the 3-dimensional notion of "volume" has to be replaced by the k-dimensional notion of the determinant of a k×k matrix).