Final answer:
To calculate the current of the circuit, use Ohm's law and the total resistance of the circuit. The current can be calculated by dividing the potential difference by the total resistance. However, the potential difference is not given in the question, so the current cannot be determined without that information.
Step-by-step explanation:
To calculate the current of the circuit, we can use Ohm's law, which states that potential difference (voltage) is equal to current multiplied by resistance. In this case, the resistor is connected in series with the bulbs, so the total resistance of the circuit would be the sum of the initial resistance and the resistor's value, which is 15.6Ω + 4Ω = 19.6Ω. Since the potential difference is not given, we cannot directly calculate the current. However, if we are given the potential difference, we can use Ohm's law to calculate it. Let's say the potential difference is V volts. We can write the equation as V = I * 19.6, or I = V / 19.6. Therefore, we need to know the value of the potential difference to calculate the current.