The way the atoms in different materials fit together can make it easier or more difficult for the electrons to move. In the following example, the electric force is provided by the voltage in a battery. You can change the resistance (in Ohms) of the material to make it easier or more difficult for the battery to move the electrons.

This activity might not be viewable on your mobile device.Interactive exercise. Assistance may be required.

Battery-Resistor Circuit
Click to Run

Source: Battery-resistor-circuit, University of Colorado - Physics