An X-ray tube is operating at 50 kV and 20 mA. The target material of the tube has mass of 1 kg and specific heat 495 J kg − 1 ∘ C − 1 . One percent of applied electric power is converted into X-rays

Question

An X-ray tube is operating at 50 kV and 20 mA. The target material of the tube has mass of 1 kg and specific heat 495 J kg − 1 ∘ C − 1 . One percent of applied electric power is converted into X-rays and the remaining energy goes into heating the target. Then

TestHub · Accepted Answer

Power P = V I = 50 × 1 0 3 × 20 × 1 0 − 3 = 1000 W . Heat into target = 99% × 1000 = 990 W . ​ d t d T ​ = 1 × 495 990 ​ = 2 ∘ C / s . ​ λ m i n ​ = 50000 12400 ​ A ˚ ≈ 0.248 A ˚ ≈ 0.25 × 1 0 − 10 m . ​ The target absorbs about 1 kW of heat, so it must have a high melting point; low conductivity would be undesirable.

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