Question

An X-ray tube is operating at 50 kV and 20 mA. The target material of the tube has a mass of 1.0 kg and specific heat $495Jk{g}^{-1\circ }{C}^{-1}$. One percent of the supplied electric power is converted into X-rays and the entire remaining energy goes into heating the target. Then

• A. A suitable target material must have a high melting temperature
• B. A suitable target material must have low thermal conductivity
• C. The average rate of rise of temperature of target would be $2^{\circ }C/s$
• D. The minimum wavelength of the X-rays emitted is about $0.25\times {10}^{-10}m$

Answer 1

Answer: (A), (C), (D)

The correct options are
A A suitable target material must have a high melting temperature
C The average rate of rise of temperature of target would be $2^{\circ }C/s$
D The minimum wavelength of the X-rays emitted is about $0.25\times {10}^{-10}m$

$P=VI=50\times {10}^3\times 20\times {10}^{-3}=1000W$
Power converted into heat = 990 W
$ms\Delta T=900\Rightarrow \Delta T=2^{\circ }/sec$
Now $\frac{hc}{{\lambda }_{min}}=eV\Rightarrow {\lambda }_{min}=\frac{hc}{eV}=0.248\times {10}^{-10}m$