Two appliances are connected in parallel to a 120-v battery and draw currents i1 = 3.0 a and i2 = 3.1 a. if these appliances are instead connected in series to the same battery, what is the total current in the circuit?

Initially they are connected in parallel, so they have the same voltage V=120 V at their ends. Therefore we can use Ohm's law to calculate the resistance of each appliance:



When they are connected in series, they are crossed by the same current I. The equivalent resistance of the circuit in this case is , so we can use Ohm's law for the entire circuit to find the current in the circuit: