To find the ammeter reading, we first determine the total resistance of the circuit. According to the sources, an ammeter consists of a galvanometer coil and a shunt resistance connected in parallel .

1. Calculate the ammeter resistance ($R_a$): The coil ($480\,\Omega$) and shunt ($20\,\Omega$) are in parallel. Their effective resistance is: $R_a = \frac{R_{\text{coil}} \times r_s}{R_{\text{coil}} + r_s} = \frac{480 \times 20}{480 + 20} = \frac{9600}{500} = 19.2\,\Omega$ .

2. Calculate the total circuit resistance ($R_{\text{total}}$): The ammeter and the external resistor ($40.8\,\Omega$) are connected in series . $R_{\text{total}} = R_{\text{ext}} + R_a = 40.8 + 19.2 = 60.0\,\Omega$.

3. Apply Ohm's Law to find the current ($I$): The ammeter reading represents the total current flowing through the series circuit . $I = \frac{V}{R_{\text{total}}} = \frac{30\text{ V}}{60\,\Omega} = 0.5\text{ A}$.