A wire of length 100 cm and diameter 4 mm is twisted by 30 degrees. Calculate the angular deflection.

Step 1: Identify the given values and the quantity to be found.
The length of the wire is $L = 100 \text{ cm} = 1 \text{ m}$.
The diameter of the wire is $d = 4 \text{ mm} = 4 \times 10^{-3} \text{ m}$.
The radius of the wire is $r = \frac{d}{2} = \frac{4 \times 10^{-3} \text{ m}}{2} = 2 \times 10^{-3} \text{ m}$.
The angle of twist at one end is $\theta = 30^\circ$.
We need to find the angular deflection (shear strain) of the wire.