To find the current in a complex circuit, it is necessary to know the

potential difference in each device in the circuit.
current in each device in the circuit.
equivalent resistance of the circuit.
number of branches in the circuit.

B

I don't like any of those choices, or the question. Where do you want to know the current? What constitutes a "device"?

To find the current in a complex circuit, you need to know the potential difference in each device in the circuit. The potential difference, often referred to as voltage, is a measure of the electrical potential energy difference between two points in the circuit. It is measured in volts (V).

To determine the current, you need to know the voltage across each device or component in the circuit. This can be obtained using a voltmeter, which measures the potential difference between two points in the circuit.

Once you have the voltage across each device, you can use Ohm's Law (V = IR) to calculate the current flowing through each device. Ohm's Law states that the current (I) flowing through a device is equal to the voltage (V) across the device divided by its resistance (R). The resistance is a property of the device, measured in ohms (Ω).

Therefore, by knowing the potential difference in each device and the resistance of each device, you can calculate the current flowing through each device. It is important to note that the current in a series circuit remains the same throughout the circuit, while in a parallel circuit, the current divides among the different branches.

Knowing the current flowing through each device is essential for analyzing and understanding the behavior of the circuit, as well as for determining power dissipation and other electrical characteristics.

The correct answer is:

current in each device in the circuit.