Which term refers to the unit of pressure defined as force per square inch?

• A. Hydraulic line
• B. Hydraulic cavitation
• C. Heat exchange
• D. Psi

Answer: (D)

Pressure is defined as force per unit area, and in many mechanical and hydraulic contexts the common unit used is pounds per square inch, abbreviated as psi. This means psi represents the pressure produced by a one-pound-force acting on a one-square-inch area. In more universal terms, one psi is about 6894.76 pascals. The other terms describe a hydraulic line (a conduit for fluid), hydraulic cavitation (a fluid phenomenon where vapor bubbles form due to low pressure), and heat exchange (the transfer of thermal energy between fluids)—none of which are units of pressure. So psi is the unit that directly matches the definition “force per square inch.”