29. Which of the following technique shall only be applied to detect discontinuitie s that open to the surface. Mana teknik yang berikut yang hanya digunakan untuk deteksi discontinuities yang open to the surface. a. prod b. head shot c. yoke d. using solenoid e. none of the above.

a

The question is about the techniques used in non-destructive testing (NDT) to detect discontinuities in materials. Discontinuities refer to any interruption in the material's structure, such as cracks or voids. The techniques listed are different methods used to apply magnetic fields or particles to detect these discontinuities.1. **Prod Technique**: This involves using a ferromagnetic probe (prod) to locally magnetize a region of the material. It is effective for detecting surface-breaking discontinuities but not for subsurface defects.2. **Head Shot Technique**: This method uses a yoke with a coil and a ferromagnetic head (like a nail) to concentrate the magnetic field. It's suitable for detecting both surface and near-surface discontinuities.3. **Yoke Technique**: A yoke is used to clamp the material and create a magnetic field. It's effective for detecting both surface and subsurface discontinuities.4. **Using Solenoid**: A solenoid is a coil of wire that acts as a magnet when electrical current passes through it. It can be used to detect discontinuities, but it's not specific to surface-breaking defects.5. **None of the Above**: This option suggests that none of the listed techniques are specific to detecting only surface discontinuities.The question asks which technique is specifically used for detecting discontinuities that are open to the surface. The prod technique is the most appropriate answer as it is specifically designed to detect surface-breaking discontinuities by using a ferromagnetic probe to magnetize the material locally and detect the presence of discontinuities through a change in the magnetic field.