Tab Electronics Guide to Understanding Electricity ... - Sciences Club

46 Chapter Two
computer system, you can purchase computer programs (software) to
perform virtually any kind of design calculations that you will probably
ever need. Unfortunately, this doesn’t mean that you can ignore electronics
math altogether. The electronics math covered in this chapter is necessary
for establishing and understanding the definite physical
relationships between voltage, current, resistance, and power.
Ohm’s Law
The most basic mathematical form for defining electrical relationships is
called Ohm’s law. In the electrical and electronics fields, Ohm’s law is a
basic tool for comprehending electrical circuits and analyzing problems.
Therefore, it is important to memorize, and become familiar with, the
proper use of Ohm’s law, just as a carpenter must learn how to properly
use a saw or hammer. Ohm’s law is expressed as follows:
E IR (2.1)
This equation tells us that voltage (E) is equal to current (I) multiplied by
resistance (R). The simple circuit of Fig. 2-13 illustrates how this equation
might be used. The value of R1 is given as 10 ohms (note the capital
Greek omega symbol is used to abbreviate the word ohm), and the current
flow is given as 1 amp, but the battery voltage (E) is unknown. By
substituting the electrical symbols in Eq. (2.1) with the actual values, E
can easily be calculated.
E IR
E (1 amp)(10 ohms)
E 10 volts
Now you can go through a few more examples of using Ohm’s law to
really get the hang of it. Note the circuit illustrated in Fig. 2-14. I have
Figure 2-13
Basic DC circuit illustrating
Ohm’s law.
–
+
E
R 1 10
I 1A