The resistance of an open circuit wire is _____.

• A. Infinite ohms
• B. Zero ohms
• C. Finite ohms
• D. Variable

Answer: (A)

An open circuit has a break in the conducting path, so no current can flow. Resistance is defined as R = V / I, and with a finite voltage but essentially no current, the ratio becomes infinite. So the resistance of an open circuit is infinite (in practice, extremely high), which is what you’d see on an ohmmeter when testing an open switch or an unconnected wire. The other possibilities don’t fit: zero ohms would mean a short, finite ohms implies a closed path with some material resistance, and variable would indicate changing resistance, which isn’t the case for an open circuit.