Electric Potential and Capacitance

Two positive charges of magnitude q are each a distance d from the origin A of a coordinate system as shown above. At which of the following points is the electric potential greatest in magnitude?

• A

• B

• C

• D

• E

The figure above shows two particles, each with a charge of +Q, that are located at the opposite corners of a square of side d. What is the potential energy of a particle of charge +q that is held at point P ?

• Zero

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A positive charge of 3.0 × 10^–8 coulomb is placed in an upward directed uniform electric field of 4.0 × 10⁴ N/C. When the charge is moved 0.5 meter upward, the work done by the electric force on the charge is

• 6 × 10^–4 J

• 12 × 10^–4 J

• 2 × 10⁴ J

• 8 × 10⁴ J

• 12 × 10⁴ J

The diagram below shows equipotential lines produced by an unknown charge distribution. A, B, C, D, and E are points in the plane. Which vector below best describes the direction of the electric field at point A ?

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• None of these, the field is zero

The diagram below shows equipotential lines produced by an unknown charge distribution. A, B, C, D, and E are points in the plane. At which point does the electric field have the greatest magnitude?

• A

• B

• C

• D

• E

A particle of charge Q and mass m is accelerated from rest through a potential difference V, attaining a kinetic energy K. What is the kinetic energy of a particle of charge 2Q and mass m/2 that is accelerated from rest through the same potential difference?

• 1/4 K

• 1/2 K

• K

• 2K

• 4K

Two parallel conducting plates, separated by a distance d, are connected to a battery of emf ε. Which of the following is correct if the plate separation is doubled while the battery remains connected?

• The electric charge on the plates is doubled.

• The electric charge on the plates is halved.

• The potential difference between the plates is doubled.

• The potential difference between the plates is halved

• The capacitance is unchanged.

The capacitance of a parallel-plate capacitor can be increased by increasing which of the following?

• The distance between the plates

• The charge on each plate

• The area of the plates

• The potential difference across the plates

• None of the above