An arc welder provides 250 amps of current when operating with a voltage of 40 volts. what is the power required by this welder

The power(P) of the circuits is the product of the voltage (V) in volts and current(I) in amperes. 
                                        P = IV

Substituting the known values to the equation,
                                     P = (250 amps) x (40 volts) = 10,000 Watts

Thus, the answer is 10,000 Watts. 

Power = VI
Where V is the voltage and I the current
P=40*250
   =10,000 watts
    =10 kilowatts