A lamp is marked 60 W, 230 V. Its tungsten filament glows at 2400 °C…

Step 1. Hot resistance. $R_{\text{hot}} = \dfrac{V^2}{P} = \dfrac{(230\ \text{V})^2}{60\ \text{W}} = 882\ \Omega$.

Step 2. The factor. $1 + 4.5 \times 10^{-3} \times (2400 - 20) = 11.7$.

Step 3. Cold resistance. $R_{\text{cold}} = \dfrac{882\ \Omega}{11.7} = 75.3\ \Omega$.

Step 4. Switching on. $I = \dfrac{230\ \text{V}}{75.3\ \Omega} = 3.05$ A. The normal current is $\dfrac{60}{230} = 0.26$ A.