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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