Hernando builds a simple DC series circuit with a standard D-cell battery and uses an ammeter to determine that the total current in the system is 3.0 A. In an attempt to increase the brightness of the bulbs in the circuit, he tries to increase the voltage by adding two more batteries (in series with the first). Calculate the new current when driven by three batteries.

I = 9.0 A

Explanation: Ohm's Law is defined as the relationship between voltage and current: in a circuit, the voltage accross a conductor is directly proportional to the current.

The constant of proportionality is Resistance, whose unit is ohm (Ω).

so, Ohm's Law is

V = R.I

It is asked for the current, so, rearraging:

When added two more batteries, the voltage of the circuit triples:

Since they are directly proportional, if voltage triples, so does current:

9.0

The new current, when driven by 3 batteries is 9.0 A.

neither accurate nor precise.