Power is measured in watts and represents the rate at which work is done or energy is used. It can be calculated using current, voltage, and resistance based on Ohm's law. Energy represents the ability to do work and is the amount of power consumed over a period of time. It is measured in joules which is equal to watt-seconds. Power indicates how much work can be done in a specific amount of time and represents the rate of doing work.

1. Power & Energy

2. Power
IVP
second/Joule(W)Watt:inMeasured 
-Rate at which energy is used or
alternatively, the rate at which work
is done.

3. •Using Ohm’s Law, you
can state the above
formula in a number of
ways:
P = I2 * R
P = V2 / R

4. Energy
• Energy is the fundamental capacity to do
work.
• Note that energy can neither be created
or destroyed, only transformed.
• Energy is the amount of power
consumed over time

5. Energy
 Energy (E) lost or gained by any system is
determined by:
E = Pt
 Since power is measured in watts (or joules
per second) and time in seconds, the unit of
energy is the watt-second (Ws) or joule (J)

6. Going Back to Power
t
W
P 
second/joule1(W)Watt1 
 Power is an indication of how much work
(the conversion of energy from one form to
another) can be done in a specific amount of
time; that is, a rate of doing work.

7. Example:
• Two resistance of 10 and 15 ohms,
each connected in parallel. The two
are then connected in series with a 5
ohm resistance. If then connected
across a 12 volt battery. What are the
current and power?