Question

what causes current?
a) movement of free electrons
b) voltage applied to a circuit
c) ground applied to a circuit
d) all of the above

Explanation:

Current is the flow of electric charge. Free - electrons are charge carriers and their movement constitutes electric current. A voltage (potential difference) applied to a circuit provides the necessary force to move these free - electrons. Grounding a circuit is mainly for safety and reference purposes and is not a direct cause of current flow. The movement of free electrons due to an applied voltage is what causes current.

Answer:

A. Movement of free electrons