Ampere Meter

Hi All
When We measure the current using Ampere Meter is the Displayed No =Ampere/Hour for example if the Ampere Meter Displayes 4A and The VoltMeter Displayes 5V (For DC Curcits) is that Mean That The load rated 20W/Hour ?

Hours have nothing to do with power dissipation nor current.

5V at 4A is a power dissipation of 20W. It could be for a micro-second or for months. The amp-meter measures current that is flowing now. The volt-meter measures voltage now. Multiply them and you have the amount of power that is dissipated now.

A rechargeable battery has an Ah rating which is how long the full charge can power a load until it is dead. Usually the current is 1/20th the rated current (they lie).

OK how We Could Measure W/h For Dc if we Have a Amp-meter and a Volt-Meter only

If your load were constant over time you could measure the current and voltage then calculate the watts. An example if you measured 10 volts and 5 amps you would have a load of 50 watts. If that 50 watts were continuous then you could say that 50 watt-hours would be consumed in an hours time.

If the current and voltage were not constant you would need a way to handle that. If you look at the relatively old mechanical watt-hour meters used by electric utilities you'll see they are quite complex.