This question on conduction of electricity through gases was quite popular among the candidates.  The performance was quite satisfactory.  However, few candidates merely mentioned ‘low pressure’ which is inadequate unless qualified with ‘very’ and temperature is not one of the factors on which the colour of light in a fluorescent tube depends as mentioned by some candidates.

The expected answers are:
(a)  A gas can be made to  conduct electricity by subjecting it to very low pressure and high voltage.
(b) The factors on which the colour of light in a florescent tube depends  

  e.g  -  the nature of the gas (inside the tube)

• the nature of coating (inside the tube)
• the pressure of the gas