If a mercury column barometer's tube has twice the diameter of a standard barometer, what will the reading indicate?

The reading of a mercury column barometer with a tube that has twice the diameter of a standard barometer will indicate the same atmospheric pressure as a standard barometer. This is because the pressure measured by a barometer is not dependent on the diameter of the tube but rather on the height of the mercury column.

The mercury column's height reflects the atmospheric pressure acting on the surface of the mercury in the reservoir. Therefore, regardless of whether the diameter of the tube is increased, the height of the mercury column accurately represents the atmospheric pressure.

In essence, the pressure exerted by the atmosphere would be balanced by the weight of the mercury column, resulting in the same reading. Thus, a larger diameter tube does not alter the fundamental relationship between atmospheric pressure and mercury height in the tube, maintaining the same pressure reading as a standard barometer.