[SOLVED] Watt=Voltage*current right?

[Qube]

guys i'm a novice in power electronics, as per my knowledge i think Watt=Voltage*current...
I have a 40 watt motor,which is powered by 18V...
so i have to find the current..
so i think current=voltage/watt? am i right..
so as per that formula,then 18/40=0.45Amps..
Are my calculations right..
then assume i have a 18V Battery,which is used in Bikes,Will it be able to supply 0.45A of current,till how long it may last..

 

[keith1200rs]

You are right that power = volts * amps but rearranging that you get amps = power/volts. So your current will be a lot higher than you think.

Keith

 

[Qube]

SO I=P/V.
P=40W
V=18
So 40/18 would be around 2.2 amps...???
A 40 watt motor running on 18V will draw 2.2 amps.
Most of the batteries are rated in Amp hours..So if we take the battery rating as 18AH..
I=2.2Amps..
18Ah/2.2Amps=~8 hours
The battery will drain fully in about 8 hours..
Do u think my calculation are correct???

 

[keith1200rs]

Yes, those calculations sound right.

Keith

 

[Qube]

^^Thank u very much...