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Open

No current flows through an open. Normally an open is created by a bad connector. Dust, bad solder joints, bad crimping, cracks in circuit board traces, create an open. Capacitors respond to DC by turning into opens after charging up. Uncharged inductors appear as opens immediately after powering up a circuit. The word open can refer to a problem description. The word open can also help develop an intuition about circuits.

Typically the circuit stops working with opens because 99% of all circuits are driven by voltage power sources. Voltage sources respond to an open with no current. Opens are the equivalent of clogs in plumbing .. which stop water from flowing.

On one side of the open, EMF will build up, just like water pressure will build up on one side of a clogged pipe. Typically a voltage will appear across the open.

Short

A voltage source responds to a short by delivering as much current as possible. An extreme example of this can be seen in this ball bearing motor video. The motor appears as a short to the battery. Notice he only completes the short for a short time because he is worried about the car battery exploding.

Maximum current flows through a short. Normally a short is created by a wire, a nail, or some loose screw touching parts of the circuit unintentionally. Most component failures start with heat build up. The heat destroys varnish, paint, or thin insulation creating a short. The short causes more current to flow which causes more heat. This cycle repeats faster and faster until there is a puff of smoke and everything breaks creating an open. Most component failures start with a short and end in an open as they burn up. Feel the air temperature above each circuit component after power on. Build a memory of what normal operating temperatures are. Cold can indicate a short that has already turned into an open.

An uncharged capacitor initially appears as a short immediately after powering on a circuit. An inductor...