The dielectric increases the electric field strength inside the capacitor, resulting in a larger voltage between the plates for the same charge. 

The following figure shows the electric field lines near two charges. Which charge has a larger magnitude?

For determining the total potential at a point due to several charges, vector addition of potential due to individual charge is needed.

Figure shows the electric field lines near two charges.  Which charge is positive? 

Three different, small charged objects are placed as shown in the figure below. The charges q1 and  q3 are fixed in place;  q2 is free to move. Given q1 = 2e, q2 = −3e, and q3 = −5e, and that d = 2.0 x 10-7 m, what is the magnitude of the net force on the middle charge q2? (e = 1.60 x 10-19 C)

What is the magnitude and direction of the force exerted on a 3.50 µC charge by a 250 N/C electric field that points due east?

The battery voltage in the following figure is 9.0 V. Determine the charge on C3.

The electric potential between the plates of a parallel-plate capacitor

Find the total capacitance of the combination of capacitors shown in the figure below.

The battery voltage in the following figure is 9.0 V. Determine the charge on C4.