shed power

You have to consider how many amps the heater draws. And it depends on what you intend to use the 10 amp outlets for. I just saw that an electric drill "draws" (*) 5-8 amps. (Bigger drill, even more ) If the heater draws 40 amps, and you use it at the same time as a drill, that is straining the limit of the 50 amp circuit. Ten 100 watt incandescent light bulbs would be safe for a 10 amp circuit, if the wiring is adequate. Use led's and it would draw much less current.
* Think of a drill "drawing" electricity through a wire like water through a hose. A circuit that is too small will restrict current flow. ("Resistance")
Resistance to current flow causes heat.
Also, the length of the wire to the shed will determine the wire gauge needed. Longer wire, bigger wire. A knowledgeable hardware store employee should be able to assist you.

thanks, so its ok to use the 50 amp as long as i dont go over 50? the heater I am looking at says its only a 30amp.

Yeah, as long as you don't exceed 10 amps on the outlets in the shed. If you use wire that is big enough, you could have 50 amp capacity at the shed as long as you didn't use the pool heater at the same time.

this is probably a silly question, but will running a 50 amp line to my shed that is using 10amp appliances burn them out or something, or is it the over way round, like trying to use a 30amp appliance to a 10 amp line.
thanks for all your help.

I understand that you are asking if "50 amp" means the wire "has" too much electricity for 10 amp appliances. No. The amp rating of a circuit indicates how much current it is capable of flowing. Like fuses in a car (or home) are made to melt if the current exceeds the capacity of the wire. A car starter requires a lot more current than a turn signal bulb. So it uses a heavy cable. The same 12 volts goes to each. So if you used a jumper cable to light a bulb, it would work. If you run a wire rated at 50 amps, you could run 5 10-amp appliances.

PS: If the pool heater is on, (30 amps), you could only use 20 amps in the shed, because 50 amps is the limit of the circuit to the pool.

thankyou very much, u have explained it very well. sorry about the poor spelling.