Magnetic Particle Inspection Level 2 Practice Exam

For a bar with an L/D ratio of four in a ten-turn coil, what is the required current?

1. 45,000 amperes

2. Unknown; more information is needed

3. 18,000 amperes

4. 1125 amperes

The correct answer is: 1125 amperes

In magnetic particle inspection, the current required for a coil is influenced by the dimensions of the part being inspected, particularly the length-to-diameter (L/D) ratio. An L/D ratio of four in a ten-turn coil suggests a relationship between the length of the part and its diameter that affects how magnetic fields can be generated and maintained within the material. To calculate the required current for magnetizing the bar, using the formula \(I = k \times (L/D) \times N\), where \(I\) is the current, \(k\) is a constant related to the material and coil design, \(L/D\) is the length-to-diameter ratio, and \(N\) is the number of turns in the coil, one can derive a proper current value. The given context describes that with this specific L/D ratio and the ten turns in the coil, the required output is relatively low compared to the other options. This value of 1125 amperes is considered suitable for effectively producing the necessary magnetic field within the bar while not exceeding operational limits that may cause overheating or damage to the coil or specimen. Thus, the calculation leading to 1125 amperes indicates a balance of sufficient magnetizing force being generated