TLE Basic Electronics

Power

What you are expected to learn

At the end of this module, you should be able to:

Define power as it relates to electric circuits.
State the relationship of current and voltage.
Solve for power consumption in an electrical circuit.
Determine the total power consumption in a series, parallel, or series-parallel circuit.

How to learn from this module

Going through this module can be both a fun and a meaningful learning experience. All you need to do is make use of your time and resources efficiently. To do this, here are some tips for you:

1. Take time in reading and understanding each lesson. It is better to be slow but sure than to hurry finishing the module only to find out that you missed the concepts you are supposed to learn.

2. Do not jump from one chapter to another. Usually, the lessons are arranged such that one is built upon another, hence an understanding of the first is essential in comprehending the succeeding lessons.

3. Be honest. When answering the test items, do not turn to the key to correction page unless you are done. Likewise, when performing experiments, record only what you have really observed.

4. Safety first. Perform the experiments with extra precaution. Wear safety gears whenever necessary.

5. Don’t hesitate to ask. If you need to clarify something, approach your teacher or any knowledgeable person.

What to do before (Pretest)

1. Define power as it relates to electricity.

2. What unit is used to measure power?

3. Calculate the missing value:

a. P ?, E =12V, I= 1 A

b. P 1000 W, E =?, I= 10 A

c. P =150W, E =120= V, I= ?

4. Current I is 2 A in a 5- R. Calculate P.

5. Voltage V is 10 V across a 5- R. Calculate P.

6. Resistance R has 10 V with 2 A. Calculate the values for P and R.

7. How much is the R of a 100-W, 120-V lightbulb?

8. How much power is dissipated by a 2-Ω R with 10 V across it?

9. Calculate P for 2 A of I through a 2-Ω resistor.

10. Suppose the resistance is 472 Ω, and the current is 875 mA. What is the power dissipation must therefore be

Lesson 7: Power

Work and energy are essentially the same with identical units. Power is different, however, because it is the time rate of doing work. As an example of work, if you move 100 lb a distance of 10 ft, the work is 100 lb 10 ft or 1000 ft·lb, regardless of how fast or how slowly the work is done. Note that the unit of work is foot-pounds, without any reference to time.

• Power (electrical) refers to how fast an electrical circuit is using up electrical energy thus power is sometimes referred to as power dissipation. Expressed more precisely, electrical power refers to how fast electrical energy is converted to other forms of energy.

• The amount of electrical power in a circuit is equal to the voltage times the current. Expressed mathematically, this relationship is expressed as,

•Power = voltage x current

•P (watts) = V (volts) x I (amperes)

• Power is the rate at which energy is delivered to a circuit.

• Power is also the rate at which energy (heat) is dissipated by the resistance in a circuit.

• Power is measured in watts.

• The total power dissipated in a series or parallel circuit is equal to the sum of the power dissipated by the individual components.

PT = P1 + P2 + P3 . . . Pn