Electricity for passenger cars pulled by diesel/steam locomotives?

I thought that electricity for passenger cars is supplied by the locomotive until I read the Car Builders'Cyclopedia (1946) eBook. I found out that passenger cars have generators driven by wheels under the cars.

There are different systems. Modern times, most of the electricity is supplied from the locomotives. However that is somewhat new, and in the passed it was either truck generators, or there would be a separate generator car to provide the power. Some of the "older" systems are still the primary use in some places of the world. If a railroad's primary focus is freight, than often their passenger service will use a non-locomotive power supply.

peter

Back in the sixties US, it seemed like you could hear something running with a fan underneath when you stepped onto any passenger car. I guess I always wondered if it was a power generator, or maybe was it heat/ac? But if the latter, then powered from where?

The "fan" was most likely the air conditioner and all cars had/have battery's.

That would make sense then, with a wheel driven generator.

EMD used to make "E" and "F" locomotives. "F" locomotives are usually used for freight trains and "E" locomotives are usually used for passenger trains. "E" locomotives are longer than "F" locomotives because the "E" locomotives supply heat and electricity to passenger cars. Is this true?

Your questions have several explanations, I will try to make it easy and from the European mode of operation that I suppose was similar in part to the American.

Steam:

The steam locomotives for passenger trains had a steam-driven electricity generator for the lighting of the train and some coupling hoses to transmit the electricity to the coaches (only for the lighting).

Diesel:

Most diesel locomotives are actually diesel-electric; A large diesel engine generates electricity to power the electric traction motors placed on the axles of the bogies and in the diesel passenger locomotives there is a converter and couplers to transmit the lighting and heating current to the train.

In both steam and diesel, the classification of passengers or freight is not only for that and it is not the subject of this thread.
Regarding the classification in diesels, for example the Alco F were for freight and the Alco P for passengers.

Coaches and wagons:

Most passenger cars had battery boxes at the bottom and a dynamo too or one in each bogie to charge the batteries.
The main purpose of these batteries was to power the lighting system of the train when it was stopped and without a locomotive.
But as I said there were many operating systems.
This system was also used by some wagons such as mechanical reefers to keep the cold at stops, although for a lot of consumption there were or are exclusive generator wagons for refrigerated trains like the Russian ones. In Spain, I have seen a platform with a couple of 20 generator containers on an isothermal container train.

I hope I have clarified your question a bit.

Regards, Javier

This is for US Railroads:

Today's standard is to power the coaches from the locomotive or a power car. This is called H.E.P. or headend power.

With steam locomotives things were somewhat different.

Usually the electric lights were powered by batteries which were recharged from a generator connected to the wheels. Heating came from the steam locomotive through a hose that had flexible couplings. There were two kinds of air conditioning systems installed. An ice system and then one that used propane in the early days. There were bunkers under the car floors for the ice.