Effects of Open and Short Circuits.

Basic Electronics
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97

resistance is now equal to the resistance of R1, or 20 Ohms.

As you know, R2 and R3 form a parallel network.

Resistance of The network

can be calculated as follows:

Given:

R2 = 100 Ohms

R3 = 0 Ohms

The total circuit current with R3 shorted is 6 amps. All of this current

flows through R1 and would most likely damage R1. Notice that even though

only one portion of the parallel network was shorted, the entire parallel

network was disabled.

Opens and shorts alike, if occurring in a circuit, result in an overall

change in the equivalent resistance. This can cause undesirable effects in

other parts of the circuit due to the corresponding change in the total

current flow. A short usually causes components to fail in a circuit which

is not properly fused or otherwise protected. The failure may take the form

of a burned-out resistor, damaged source, or a fire in the circuit

components and wiring.

Fuses and other circuit protection devices are installed in equipment

circuits to prevent damage caused by increases in current.

These circuit

protection devices are designed to open if current increases to a

predetermined value.

with the circuit or portion of the circuit that the device is protecting.

When the circuit protection device opens, current flow ceases in the

circuit.