If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

### Course: Class 10 Physics (India)>Unit 3

Lesson 7: Electric power and heating effect of current

# Electric power & energy

Let's learn how to calculate electric power delivered & consumed in any circuit.  Created by Mahesh Shenoy.

## Want to join the conversation?

• 1)why is kWh a commercial unit of power?
2)does the concept of heating effect of electric current work in these LED bulbs?
(1 vote)
• 1) kWh is not the commercial unit of power. It is the commercial unit of energy. Why? Because we use a lot of energy, and watt-second (power 'watt' * time 'second') is not sufficient (or else our power bills would run into hundreds and millions of watt-seconds!)

2) Contrary to popular belief, LEDs do generate heat, even though it's much, much lesser than other traditional bulbs. Its technology uses the maximum energy applied to it and converts it into light, leaving less heat energy.

Hope this helps. :)
• At ,he said that P=V*I. This also means that Voltage is inversely proportional to current. But ohm's law (V=I*R) tells that voltage is directly proportional to current. Isn't this a contradiction?
• The equation P=V⋅I does not imply an inverse relationship between voltage (V) and current (I). Instead, it indicates that power (P) is directly proportional to the product of voltage and current.
In Ohm's Law, V=I⋅R, the relationship between voltage (V) and current (I) is indeed direct and proportional. The constant of proportionality is the resistance (R).
There is no contradiction between these two equations. The power equation P=V⋅I provides a general relationship between power, voltage, and current, while Ohm's Law (V=I⋅R) specifically applies to resistive electrical circuits.

#ChatGPT_OP
• At he says we don not pay for "voltage or current but energy we consume". But basically energy provided is what we call volts.
For eg:5v is equal to 5 joule of energy per coulomb
(1 vote)
• Hey there,
I had a similar question and I assume the answer is the same, quite simple really,
By energy we consume he means total energy,
Say 5V is the magnitude of the source,
that isn't the total amount of energy consumed by us but rather energy consumed for 1C,
I guess it's safe to say that no-one would use only 1C.
the total amount of energy used by a device =VQ has to be the same as total amount of energy produced (by conservation of energy).
Think about what I have replied and you may get the total answer,
Hope this helps
and if I'm wrong do let me know.
(1 vote)
• what is energy? like charge is something that electrons and protons possess that causes them to attract and repel each other. a definition like this one of energy
(1 vote)
• I really don't get why we pay for the energy we use and not for the voltage we use. Could someone please elaborate on it?