BASIC ELECTRONICS - OD1633 - LESSON 1/TASK 2
(b) Product Over the Sum Method.  A convenient method for finding
the equivalent, or total, resistance of two parallel resistors is by using 
the following formula:
This  equation,  called  the  product  over  the
sum
formula,
is
used
so
frequently it should be committed to memory.
Example: What is the equivalent resistance of a 20 Ohm and a 30 Ohm resistor 
connected in parallel, as in figure 52 on the following page.
Given:
R1 = 20 Ohms
R2 = 30 Ohms
circuit are essentially the same as those used for the series circuit.
Since  power  dissipation  in  resistors  consists  of  heat  loss,  power 
dissipations are additive, regardless of how the resistors are connected in 
the circuit.  The total power is equal to the sum
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