## Self Test on SI Units

### Quiz

A homogeneous equation means:

- an equation in which the units on the left hand side are the same as the units on the right hand side;
- an equation in which the units on the left hand side are the different to the units on the right hand side;
- an equation that can be broken down to different terms;
- an equation that gives out a number with no units.

Refractive index is a quantity used in the study of light. It is given by the equation:

Refractive index = speed of light in air ÷ speed of light in glass.

Which one of these gives the correct units for refractive index?

- m s
^{-1}; - m
^{2} s^{-2}; - s
^{2} m^{-2}; - No units

Which one of these is a base unit?

- kilogram;
- joule;
- volt;
- newton.

In a physics text-book, you see the symbol
*A* in italics and in
Times New Roman font. This is most likely to mean:

- current in amperes;
- altitude in metres;
- area in square metres;
- a reference to an alpha particle.

Elsewhere in the text book you see the term ‘5 cd’ in lower case, and in normal font. This is most likely to refer to:

- a recording medium for music;
- the unit for light intensity, candela;
- a unit prefix, centi-deci, which means one thousandth;
- a small diesel hatchback car, made by a far-eastern manufacturer.

Density is defined as mass per unit volume. Which one of these units is correct?

- kg m
^{3}; - kg m
^{-3}; - m
^{3} kg^{-1}; - m kg
^{-3}.

In a physics text book problem, you are given a quantity of 5.5 ms. This means:

- 5.5 metres;
- 5.5 metre seconds;
- 5.5 megaseconds.
- 5.5 milliseconds;

Which one of these is the correct conversion for 25 GW?

- 25 × 10
^{3} W; - 25 × 10
^{6} W; - 25 × 10
^{9} W; - 25 × 10
^{12} W.

Later on in your course, you have correctly worked out the capacitance of a capacitor as 4.7 × 10^{-9} F. With a prefix, this is:

- 4.7 pF;
- 4.7 nF;
- 4.7
F;
- 4.7 mF.

The density of iron is 7.6 g cm^{-3}. In SI units, this is:

- 7.6 kg m
^{-3}; - 76 kg m
^{-3}; - 7600 kg m
^{-3}; - 7.6 × 10
^{6} kg m^{-3}.