Electric Power:

Objectives:

1.    Describe power and its measurements.

2.    Explain the units of power.

3.    Calculate power, work, and time using the formula; P = W/t.

Key Terms:

power    watt

Resources:

Notes:

Electric Power:

We can remember from earlier in the semester that power indicates the rate (how fast) that work is being done.  The same is true of electricity but in this case it refers to how much electrical work is done by a light or motor.

• It is the rate at which electrical work is being done
• It is still the amount of work per unit time but is figured using different variables

Formula:    Electric Power = current x voltage (I x V or C/s x J/C) = J/s or Watts

• Remember that the unit for work is the Joule and that the second is the unit for time
• The unit for power is the Watt (W) (www.atob.org.uk/More%20illustrations/ Electric-power.gif)

Electric Energy:

Electrical energy is defined as the ability of electricity to do work.   Although we have previously discovered that energy comes in many forms if work has been performed by an electrical device electrical energy was present.  Remember that when you plug an item into an electric source you have stored energy (V) in that object.  You have given that object the ability to cause change or to do work.  When you turn it on you give power.  The amount of time it is on reflects the energy used.

Energy = power · time        or         E = P · t        or        E = I x V x t        or        C/s x J/C x t

Energy is measured in kilowatt hours  Electric safety:

1.              Never handle appliances while you are standing in water

2.              Never run wires under carpet

3.              Never overload a circuit by connecting too many appliances to it

4.              Always repair warn of frayed wires

5.              Never stick your fingers in an electric socket

Never come close to power wires on power poles or fallen wires

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