A wave front has the form of a surface of a sphere
According to Joule's Law, we have the relationship between charge, voltage, and current:
W = Vq
where q is the charge
V is the voltage or the potential difference
W is the work done
From the given values and rearranging the equation:
V = 10J / 4.0x10^-2
V = 250 V
The voltage difference is 250 V
As the radius increases the circumference increases.
The more powerful an appliance is, the more amounts of energy it uses. For instance a jack hammer that does not create a lot of destruction or change does not use a lot of energy. If a jack hammer that creates a lot of destruction and change probably uses a lot more energy and makes more sound.