The flow of electrical charges in this is caused by energy differences and voltage
a) voltage b) insulator c) current d) circuit

A difference in voltage

Or potential difference

Explanation:Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential between two points. The difference in electric potential between two points in a static electric field is defined as the work needed per unit of charge to move a test charge between the two points.

Electric current is the flow of electrons in a conductor. For example, the first element has more positive charges, so it has higher potential. On the other hand, the second element has charges that are more negative so it has lower potential. The difference between two points is called potential difference

astronomers such as edwin hubble.