ISA Certified Control Systems Technician (CCST) program


Certified Control System Technicians (CCSTs) calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables.

CCST question

A circuit has a 100 Ω resistor, a 50 Ω resistor, and a 200 Ω resistor all in parallel with each other. What is the total resistance of the circuit?

A. 28.6 Ω
B. 35.0 Ω
C. 175 Ω
D. 0.28 M Ω

CCST Answer

The correct answer is A, 28.6 Ω. To find the total resistance for resistors in parallel, use the equation:

Reference: Goettsche, L.D. (Editor), Maintenance of Instruments and Systems, Second Edition, ISA, 2005.