Question

what isthe role of kink in a clinical thermometer

Answer 1

There is a slight kink or bend at the edge of the thermometer to make sure that the mercury doesn't fall down after it is taken out of the mouth.

Answer 2

$\sf \huge \underline{answer} \implies$

Kink in the Mercury thermometer helps to prevents the falling of mercury present in capillary tube into bulb. It ensures that the user takes the correct reading of temperature. That's the reason a person before taking a new reading must give a sudden shake to the clinical thermometer so that the mercury level comes to normal.