A generator gives an average electrical power of 40 W to a lamp while its coil turns 30 times each…

Step 1. The angular speed. $\omega = 2\pi f = 2\pi \times 30\ \text{Hz} = 188.5\ \text{rad/s}$.

Step 2. The torque. We want $\tau$, so $\tau = \dfrac{P}{\omega} = \dfrac{40\ \text{W}}{188.5\ \text{rad/s}} = 0.212\ \text{N m}$.

Step 3. The work in one turn. One turn takes $\dfrac{1}{30}$ s. So $W = P \times \dfrac{1}{30}\ \text{s} = 40\ \text{W} \times 0.0333\ \text{s} = 1.33\ \text{J}$.