Let’s Get Physics-l: Electrical Power

Electrical power is something we are all incredibly familiar with. The device your using is currently transferring stored chemical energy to electrical energy so you can read this. Whether or not that’s a good thing I’ll leave to you to decide.

Power is the rate at which energy is transferred from one form to another, sort of like taking materials and making something out of it in hour or so. You start with these materials and, over time, build something new out of them. But that’s a really dull example.

Well that makes for a shocking turn of events

Here we see some classic Spider-Man action. Though Spider-Man’s Spider Sense is pretty impressive Spider-man just missed dodging an electric blast from Electro. It hits our beloved web head right in the chest, flinging him a few metres into a wall. Ouch, even for a superhero. The wall was a few metres behind Spider-Man so he was in the air for a good 5 seconds over which time electrical energy from Electro was transferred to kinetic energy as Spider-man flew through the sky.

We measure power in Watts (What? Exactly (Sorry)). A device powered by 1 Watt will transfer 1 Joule of Energy from one form to another in 1 second.

We can calculate the amount of energy transferred (or work done) by taking power into account:

E = P x t


  • E – Energy in Joules
  • P – Power in Watts
  • t – Time in Seconds

This equation applies to all forms of energy be nuclear or gravitational potential. However, electricity is a bit extra in that it needs a couple more equations. First a quick refresher:

We know that we can calculate Work Done as a product of Charge and Voltage, W = VQ. Charge can be calculated as a product of Current and Time, Q = It. We can then substitute the latter into the former to create:

W = V x I x t


  • W – Work Done (J)
  • V – Potential Difference (V)
  • I – Current (A)
  • t – Time (s)

This equation isn’t too bad if you just get with it (Sorry). These aren’t the only equations we use that involve power, though.

We now know that power is work done (or energy transferred) per unit time. With this in mind, we represent power as:

P = I x V


  • P – Power (W)
  • I – Current (A)
  • V – Potential Difference (V)

If we know throwback to Ohm’s law, V = I x R, we can derive a further 2 equations from the one given above:

P = I² x R

P = V²/R

With all these equations under our belts, we can calculate a fair bit given the right variables.

In terms of real world applications, the appliances we use rely heavily on electrical power. Be it light bulbs (electrical to light) or kettles (electrical to heat), electrical power is something we would struggle to live without now a days.


  • Electrical Power – Rate of energy transfer
  • E = P x t
    • E – Energy (J)
    • P – Power (W)
    • t – Time (s)
  • W = V x I x t
    • W – Work Done (J)
    • V – Potential Difference (V)
    • I – Current (A)
    • t – Time (s)
  • P = I x V
    • P = I² x R
    • P = V²/ R

There we have it, Electrical Power. If you have any thoughts or questions please feel free to leave them in the comments and I’ll do my best to help. Thank you.

(The Characters used are property of Marvel Comics. I in no way lay claim to them.)







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