# Problems with Charges, Circuits, Electric and Magnetic Fields

## AP Physics C Practice

Question 1: The electric potential of a region of space is given by V(x,y,z) = 2x + 3y + 1/z. Which of the following statements must be true?

Question 2: Two resistors and a capacitor are connected to a 20V source as shown below. What is the charge on each conducting plate of the capacitor?

Question 3: Four point charges are located in free space on a circle C of radius r, as shown below. What is the magnitude of the electric field at the origin due to the four charges, if the area of the circle is A = π, and k is Coulomb's constant?

Question 4: Two charged particles enter a region with the same speed, v, as seen in the figure below. After entering the region, both particles move in the same direction. If the positive charge accelerates and the negative charge decelerates, the region could have:

Question 5: A sphere of uniform charge density and radius R is charged with a positive charge +Q. The electric field at a R/2 distance from the sphere center is E. What is the electric field at a distance of 2R from the center?

Question 6: Capacitor C1 is created with two parallel square conducting plates of area A, dielectric of relative permitivity ε and distance between the plates d1 = 3mm. Capacitor C2 is created with two parallel square conducting plates of the same area A, dielectric of relative permitivity ε and distance between the plates d2 = 1mm. If Cs is the capacitor equivalent to C1 in series with C2 and Cp is the capacitor equivalent to C1 in parallel with C2, then Cs/Cp is equal to:

Question 7: A voltage source E is connected to four resistors as shown in the figure below. What is the value of the current that flows through the the voltage source E?

Question 8: A positive charge travels through a region with a magnetic field B, with a speed v, as shown above. If the force on the particle due to the magnetic field is F, which of the following orientations of the force must be true?

Question 9: A wire bent at a 90o angle carries a current i, as shown below. The magnetic field at point A:

Question 10: A voltage source E is applied to a circuit formed by a resistor R and an inductor L connected in series. What is the current in the resistor at the time t = L/R after the switch S1 is closed?

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