What happens to the current when only a single additional bulb is added to a circuit with a single cell and bulb at 0.2A?

In a series circuit, adding another bulb increases the total resistance of the circuit. According to Ohm's law, where current (I) is equal to voltage (V) divided by resistance (R), an increase in resistance will result in a decrease in current if the voltage remains constant.

When the single additional bulb is connected in series with the existing bulb and cell, the total resistance increases because both bulbs contribute to the overall resistance. Since the cell's voltage does not change, and the added resistance due to the new bulb is significant enough, the current flowing through the circuit must decrease.

As a result, if the original current was 0.2A, the new configuration with two bulbs in series will lead to a reduction in current, often close to half of the original value. Thus, the current is likely to decrease to around 0.1A, consistent with the scenario where you've introduced an additional resistance without changing the power supply's voltage.

This understanding of how resistance affects current in a series circuit clarifies why the current would decrease significantly when an additional bulb is added.