If you're concerned about the state of your wiring then round up a voltmeter.
Measure the AC voltage with minimal load, then measure with that vacuum or hand iron turned on. A microwave oven would be another high load appliance if you don't vacuum carpet or iron clothes.
If nominal voltage is around 117, then a 2% (considered acceptable) drop is about 115. 113 might be OK but any lower means the wire is getting pretty hot under load and the wiring is in need of upgrading or you need to divide your load between different circuits. Connecting to different circuits could, however result in one of those nasty A/V "ground loops".
Technically (but universally ignored) a TV is supposed to be on an appliance circuit and not a lighting circuit. Lighting circuits tend to connect all of the outlets in series, one after the other; so the last in series might have an extra 50 - 100 feet of wire from the first and jump through the sockets in several locations. (all permissable under code but bad for heavy appliances) In this case you want the TV on the first or second outlet and not the fifth or sixth. Do your voltage testing on more than one outlet in the room because of this.
