Question

Why does a clinical thermometer have a kink?

Answer 1

"Clinical thermometer" has a kink to prevent the 'mercury' from falling 'back' in the bulb.

EXPLANATION:

The kink holds the mercury in place in the capillary and helps to take the temperature reading.

The kink also separates the mercury at high temperature from the mercury at low temperature and therefore helps in taking the temperature reading. When the 'thermometer' is taken off from the patient’s mouth, the kink doesn't  allow the mercury to fall back and therefore temperature can be recorded.