Units, Measurements and Scientific Instruments — SI Units and What Measures What

Almost every general science paper carries one or two questions on units and instruments, and they are the cheapest marks in the whole paper. There is nothing to derive, nothing to calculate, no diagram to read. Either you know that a lactometer checks milk or you do not.

That also makes them the marks most often thrown away, because the setter does not test knowledge — the setter tests confusion. Hygrometer and hydrometer differ by one letter and measure completely different things. A barometer, a manometer and a sphygmomanometer all measure pressure, of three different things. Anemometer, ammeter and altimeter sound alike and share nothing.

So do not revise this as a list of instruments. Revise it as a list of pairs that get mixed up. Learn the two members of each pair together, with the difference said aloud, and the trap stops working on you.

1. Which of the following is NOT an SI base unit?

2. The purity of milk is checked with a:

3. The speed of the wind is measured by an:

4. The SI unit of magnetic flux is the:

5. One parsec is approximately equal to:

6. Very high temperatures, such as those inside a furnace, are measured by a:

7. A fathometer is used to measure:

8. One horsepower is approximately equal to: