# How can we define the energy stored in a (conservative) force field?

I have come to know from my textbook that energy is stored in the E-field of a capacitor, in the B-field of an inductor and so on. Take the example of an inductor. The derivation bewilders me completely. From Kirchhoff's Loop Rule, we take the the voltage drop along the inductor, multiply by current then integrate it wrt time to get the energy stored in an inductor. They say that the energy is stored in the B-field of inductor.

Analogically lets take the same derivation for a freely falling body opposed by drag (ohmic resistor) accelerating downwards due to g (inductor). We can find the work done by G-field and say that the gravitational potential energy of the body changes by this much. Can we say that this much energy is being stored in the gravitational-field?

In the same way the term $$\frac{1}{2} L \,i^2$$ represents the energy change of the charge flowing per unit time through the inductor. How does this relate with the energy stored in the inductor or in the B-field?

So my question, how can we define the energy stored in a force field, or at least visualise it, and why is it needed to consider that this is being stored in the field?

• In your analogy, the energy is stored in the gravitational field when you elevate the object. The object free-falling is like the capacitor discharging. – glS Feb 3 '15 at 8:16
• yes, but the scenario remains the same. Energy is being released by the field. – Sagnik Feb 3 '15 at 8:21