## Saturday, October 01, 2016

### 5.3 Power

This is the third week of Module 5 in the Navy Basic Electricity and Electronics series. This module is on the relationships between current, voltage, and resistance. The first two sections were:

5.1 Voltage, Resistance, and Current
5.2 Ohm's Law Formula

1. "Power is the rate of doing work" (66), the amount of work done by the electricity (in this case) in a given time. We might express this relationship with the formula:
P = W/T

Another way to put it is to say that electrical power is the rate of converting electrical energy into some other form of energy (e.g., heat).

2. Electrical power is measured in watts (watts having the symbol w). A 100 watt bulb burns brighter, has less resistance, and dissipates more power than a 60 watt bulb.

3. Power equals voltage times current P = EI .
• If we substitute in E = IR from the previous lesson, we get P = I2R .
• We can also do a little algebra and come up with P = E2/R
• You use different versions of the relationships depending on what information is given.
*4. Read at your own risk. Another tidbit in this section is that the amount of heat produced by a resistor is the power times the amount of time or I2RT . If you think of the original formula P = W/T, this formula suggests that work relates in some way to the heat given off.

The section doesn't really explain what work is when it comes to electricity. I guess that is something for a later module. In terms of mechanical energy, work is the force times the distance. I am not remembering exactly how that plays out with electricity, but I seem to remember that the same unit of work is used, the joule.

#### 1 comment:

Sridhar Chandrasekaran said...

Nice post. I think you love physics so much. I enjoyed the post. I refer this blog to my science students. thanks