Difference between Energy and Power: Building a Simple Intuition

So today I was reading up on signal energy and signal power for my Signal Processing class, and I came upon this conundrum that I occasionally have, I am aware of the terms Energy and Power, but what do they mean.

Okay for starters, just to get this out of the way, signal energy and signal power do not represent energy and power in the traditional sense, which is kind of confusing and can potentially throw you off, but it is this latter energy and power I want to talk about.

Now I’m not going to build a super critical definition of energy nor power, this is just a sort of intuition building exercise for those occasions when definitions get fuzzy because I have been reading too far and wide.

Energy is defined as the ability to do work, and its units are joules or Watt-hours.

On the other hand, power is defined as the rate of doing work and its units can be joules/s, or Watt.

Another point to note is that energy can be stored, and transformed from one form to another, while power cannot be stored.

So what’s a simple model to solidify this concept of energy and power? Because it is one thing to give definitions but it also helps to give examples to aide in gaining intuition.

Let’s say you have a 5 Watt lamp, meaning that for the lamp to be illuminated, it has to draw 5 Watts from whatever source you’ll provide; let the source be a battery. If you desire to keep the bulb illuminated for an hour, then the amount of energy you need is 5 Watt hour. A 5 Wh battery should let your 5 Watt lamp run for 1 hour, ideally.

If you trade your 5 Watt lamp for a 1 Watt lamp and still maintain your 5 Wh battery then you can illuminate your 1 Watt lamp for 5 hours.

These are the conclusions that can be drawn from this discussion: if both your 5 Watt lamp and 1 Watt lamp are to run for one hour on similar 5 Wh batteries, the 5 Watt lamp will consume more energy, 5 Wh, than the 1 Watt lamp, 1 Wh. However, if the 5 Watt lamp runs for 1 hour and the 1 Watt lamp runs for 5 hours, both lamps will have ended up consuming the same amount of energy, 5 Wh. Instantaneously, the 5 Watt lamp draws more power from a 5 Wh battery when compared to a 1 Watt lamp’s power draw.

You could also go on and conclude that your energy is stored in the battery as chemical energy, which is then converted to electrical energy.

Typically, power is drawn and energy is consumed.

So that’s a relatively simple way to look at energy and power for the purpose of building an intuition 😌.

2 thoughts on “Difference between Energy and Power: Building a Simple Intuition

  1. Thank you so much for sharing your knowledge and experience with electronics and the ebaz4205 card. I truly do appreciate this. One point, on you post about energy and power you wrote: (However if the 5 Watt lamp runs for 1 hour and the 1 Watt lamp runs for 5 hours, both lamps will have ended up consuming the same amount of power, 5 Wh.) Did you mean Energy and power or, am I missing something?

    1. Hi Brian, thanks for pointing this out, it should be “consuming the same amount of energy”.

      I’m also glad to know that the EBAZ4205 post helped you out.

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