Question

Spidermans nemesis electro delivers 4kj of electrical energy in half a second how much power does it draw from the mains?

Answer 1

Answer:

8 KW

Explanation:

Energy = 4 k J = 4000 J

t = 0.5 second

Power is defined as the rate of doing work.

Power = energy / time = 4000 / 0.5 = 8000 W = 8 KW

Answer 2

Power delivered = (energy delivered) / (time to deliver the energy)

Power delivered = (4,000 J) / (0.5 sec)

Power delivered = 8,000 watts

I'm a little surprised to learn that Electro draws his power from the mains.  This is VERY good news for Spiderman !  It means that Spiderman can always avoid tangling with Electro ... all he has to do is stay farther away from Electro than the length of Electro's extension cord.

But OK.  Let's assume that Electro draws it all from the mains.  Then inevitably, there must be some loss in Electro's conversion process, between the outlet and his fingertips (or wherever he shoots his bolts from).

The efficiency of Electro's internal process is

(power he shoots out) / (power he draws from the mains) .

So, if he delivers energy toward his target at the rate of 8,000 watts, he must draw power from the mains at the rate of

(8,000 watts) / (his internal efficiency) .