"Colin" wrote
| I have several transformers plugged in around the house (laptop,
| battery chargers, musical keyboard, etc.) I was wondering whether
| they drew power when the device plugged into them was switched off?

A little.

| Should I switch off the plug sockets that the transformers are plugged
| into when the devices plugged into the transformers are not being used?

If you believe the government television campaign on at the moment showing a
mobile phone charger starting to smoulder - yes.

Owain