The Science Quiz | SI-derived units

Construction tape measure on a wooden floor
| Photo Credit: andreygonchar

Questions:

1. X is the derived unit used to measure solid angles. 1 X is roughly 3,283 square degrees. More generally, it’s the amount of solid angle a unit area on a unit sphere’s surface subtends at the sphere’s centre. Name X.

2. The unit of this derived unit is squared current times the fourth power of the second per kilogram per squared metre. A capacitor with capacitance equal to one of this unit can store an electric charge of one coulomb when the potential difference between the two plates of the capacitor is one volt. Name this unit.

3. Y measures the density of magnetic flux, or the number of field lines of the magnetic field passing through a given area. It was named in honour of a famous Serbian-American engineer. In this unit, the strength of the earth’s magnetic field is around 32 micro-Y. Name Y.

4. This unit is named for a Swedish medical physicist who did important work on the biological effects of radiation, and is important in dosimetry and radiation shielding. One of this unit stands for one joule of radiation energy being deposited in one kilogram of biological tissue. Name it.

5. Z is a derived unit used to specify the catalytic activity of an enzyme. One Z means the conversion of one mole of some substance per second. (One mole is around 602 billion trillion atoms, molecules or any other similar entity being converted.) Name Z.

Visual:

Name this man for whom the unit of magnetic flux is named. This unit per squared metre is the answer to Q3.

Answers:

1. Steradian

2. Farad

3. Tesla

4. Sievert

5. Katal

Visual: Wilhelm Weber