When water is injected around a plasma stream, what is the most likely effect on the plasma column?

• A. The plasma column remains unchanged as water has no effect.
• B. The plasma column expands because water increases ionization.
• C. The plasma column contracts due to cooling and increased recombination.
• D. The plasma column becomes more luminous due to water injection.

Answer: (C)

Verified step by step guidance

1. Understand that a plasma column is a region of ionized gas where ions and electrons coexist, maintained by high temperature and energy input.
2. Recognize that injecting water around the plasma introduces a cooler substance, which can absorb heat from the plasma, leading to a decrease in temperature around the plasma column.
3. Recall that plasma stability and size depend on the balance between ionization (which sustains the plasma) and recombination (where ions and electrons recombine to form neutral atoms). Cooling promotes recombination.
4. Conclude that the cooling effect from water injection increases recombination rates, reducing the number of charged particles and causing the plasma column to contract.
5. Therefore, the most likely effect of injecting water around a plasma stream is contraction of the plasma column due to cooling and increased recombination.