A uniform capillary tube closed at one end, contained air trapped by a thread of mercury 85 mm long. When the tube was held horizontal, the length of the air column was 50 mm. When it was held vertically with the closed end downwards, the length was 45 mm. Find the atmospheric pressure in Pa. (Density of mercury = 14 x 10^3 kg/m3 ) Solutions:

The concepts needed to solve such questions Length increases, resistance increases and vice versa. Finding resistors in parallel and in series.

Sensitivity of the ammeter means that how small a current the ammeter can measure. Example, if the original set up is 0.2 A per division, and the modified set up can measure up to 0.1 A per division, so we say the latter one is more sensitive as it is able to measure smaller change in the currrent.

These two questions are actually the same. Q23 is from 2010 Pure Physics P1 while Q11 is from 2014 Sci Physics P1. Take a look at these 2 questions. If you are not sure, view the video below for the explanation. Answer to Q23: Option A Answer to Q11: Option D If you do not know how to answer these 2 questions, view this video and also refer to the lens summary below.