An open in a circuit is:

• A. A low resistance path around a load device
• B. A closed switch
• C. A lamp that is illuminated
• D. A break in the circuit that prevents current flow

Answer: (D)

An open circuit means there is a break in the conducting path so current cannot flow. Without a continuous loop, electrons can’t complete their path back to the source, so the current is essentially zero even though a voltage may be present on one side of the break. In practical terms, this happens when a switch is off, a wire is broken, or a fuse has blown. Because no current flows, the load doesn’t operate. This is different from a short circuit, which creates a very low-resistance path that causes a large current to flow, and from a normal closed circuit where current can flow and a device like a lamp lights.