Question 1 QMED01 - Junior Engineer

The Correct Answer is D **Why option D ("length of the stroke") is correct:** The displacement (volume) of a cylinder is the volume swept by the piston as it moves from its outermost position (Bottom Dead Center, or BDC) to its innermost position (Top Dead Center, or TDC). This volume is fundamentally a calculation of a cylinder's volume ($V = \pi r^2 h$). In the context of an engine: 1. The base area is determined by the piston's diameter (or **bore**, $d$), which gives the radius $r$. 2. The height ($h$) is determined by the distance the piston travels, which is the **length of the stroke**. Therefore, the cubic inch (or liter) displacement of a cylinder is calculated using the diameter of the piston (bore) and the length of the stroke. **Why the other options are incorrect:** * **A) length of the crankshaft:** The crankshaft's overall length relates to the number of cylinders in the engine, but it does not directly determine the volume displaced within a *single* cylinder. The displacement is determined by the throw (offset) of the crankshaft journal, which sets the stroke length. * **B) volume of the clearance space:** The clearance space (or combustion chamber volume) is the volume above the piston when it is at TDC. This volume is critical for calculating the compression ratio, but it is **not** included in the calculation of the engine's displacement (swept volume). * **C) weight of the piston:** Piston weight is important for balancing the engine and determining inertia forces, but it has no bearing on the geometrical calculation of the cylinder's displacement volume.