Dave Plowman (News) wrote:
In article ews.net,
Doctor Drivel wrote:
Waiting at a traffic lights with the running engine, the efficiency of a
petrol engine is 0%

In practice not if it's running air con or heating.

As far as exrtracting motive power, its 0%.

When an electric car is at the traffic lights it is at 100% efficiency.

In practice not if it's running air con or heating.

Its also 0%..it may be 0% of nothing of course. ;-)


BTW - love the idea of a stationary car being 100% efficient. So a car
with no engine at all is 100% efficient...


Indeed. 0/0 is anything you care to choose between 0 and 100%.