When a current flows through a metal wire, the moving charges are

Which of the following changes will increase the capacitance of a parallel-plate capacitor? (There could be more than one correct choice.)

Two tiny grains of sand having charges of 4.0 μC and -4.0 μC are situated along the x-axis at x1 = 2.0 m and x2 = -2.0 m. What is electric potential energy of these grains relative to infinity? 

The length of a certain wire is doubled and at the same time its radius is reduced by a factor of 2. What is the new resistance of this wire?

An ideal parallel-plate capacitor consists of two parallel plates of area A separated by a distance d. This capacitor is connected across a battery that maintains a constant potential difference between the plates. If the separation between the plates is now doubled, the magnitude of the charge on the plates will

The figure shows a group of three particles, all of which have charge Q = 8.8 nC. How much work did it take to assemble this group of charges if they all started out extremely far from each other? 

The length of a certain wire is kept same while its radius is doubled. What is the new resistance of this wire?

As a proton moves in a direction perpendicular to the electric field lines

The three point charges +4.0 μC, -5.0 μC, and -9.0 μC are placed on the x-axis at the points x = 0 cm, x = 40 cm, and x = 120 cm, respectively. What is the x component of the electrostatic force on the -9.0 μC charge due to the other two charges? 

A hydrogen nucleus, which has a charge +e, is situated to the left of a carbon nucleus, which has a charge +6e. Which statement is true?