electrical
Most of my electronic appliances are 5 A based, this includes my Desktop PC, external hard-drives, Laptop and TV but the socket I have are 10A/20 A one. Could there be a problem connecting the 5 A plugs into these 10 A/20 A socket ? I live in India where power supply is rated at 230 V Ac/50 Hz.
Additional Info –
The socket is a 5 pin 10A/20A Anchor (a brand) socket.
It depends on the power rating of the water heater. From an earlier question, I see that you live in China, so your electrical supply is 220 VAC/50 Hz. That means that the maximum power draw on a 10 A circuit is 2.2 kW (220 V * 10 A). In general, you should draw less to allow a safety margin, if the water heater uses more than about 2 kW you should get it rewired because you'll be coming close to the maximum rating of that circuit.
Note: I'm not even considering the presence of other appliances on that bathroom circuit (lights, electric razors, electric toothbrush chargers, etc.).
Based on the additional info in the question, if you only use the 1000 W and 1500 W modes on the heater, the existing wiring should be sufficient. If there's a way to prevent people from using the highest setting (like mounting the whole heater in a box where it can't be changed inadvertently), you should be OK.
Assuming this plug (a BS 1363)
and this BS 546 socket
To convert a 1363 plug to a 546 socket, this fused adapter (13A) can be safely used:
Best Answer
There shouldn't be, as a rule of thumb you'd normally want them to match, but you aren't likely to run into too many problems.
The only real big problem I can see is that if one of your 5amp devices were to short out completely, the 15/20amp breaker/fuse may not trip so your device would just sit there frying the poor 5amp socket which could cause a fire.
So, assuming you put in a lower rated fuse on the wire as well (or buy a socket with a fuse built in) it shouldn't be an issue, but I'd definitely refer to your local building codes for advice.
Hopefully someone more versed in practical electronics can help you, I've always been more of a low-power guy myself.
EDIT** Adding a few sources as I find more. First is this manual from OSHA in America, read pages 13-15 for the relevant information.