Review 2

Example 1 How does the electric field vary with distance for: a) a point charge b) a charged wire c) an infinite charged sheet

Example 2 Two concentric imaginary spherical surfaces of radius R and 2R respectively surround a positive point charge Q located at the center of the surfaces. When compared to the electric flux Ф through the surface of radius R, the electric flux through the surface of radius 2R is: A) ¼ Ф B) ½ Ф C) Ф D) 2 Ф

Example 3 An uncharged spherical conducting shell surrounds a point charge – q at its centre. Then a charge +3q is placed on the outside surface of the shell. When static equilibrium of the charges on the shell is reached, the charges on the inner and outer surfaces of the shell are respectively: A) –q and 4q B) –q and 2q C) +q and 4q D) +q and 2q

Example 4 Two parallel conducting plates in a vacuum carry equal and opposite charges. When a dielectric is inserted between the plates, the potential difference between the plates: A) Decreases. B) Increases. C) Doesn’t change. D) Is always zero, since the charges are equal and opposite.

Example 5 A negatively charged particle is moving in the +x-direction when it enters a region with a uniform electric field pointing in the +x-direction. Which graph gives its position as a function of time correctly? (Its initial position is x = 0 at t = 0.)

Example 6 Which one of the diagrams below is not a possible electric field configuration for a region of space which does not contain any charges?

Example 7 The black dot represents current coming out of the page. Which path would give us a positive integral in Ampere’s Law, S 1 or S 2 ? S1S1 S2S2

Example 8 The figure shows an LR circuit with a switch and a 240-volt battery. At the instant the switch is closed the current in the circuit and the potential difference across the inductor (between a and b) respectively are: A)0 A, 0 V B)0 A, +240 V C)0.024 A, 0 V D)0.024 A, +240 V

Example 9 A bar moves on two frictionless rails, as shown, in a region where the magnetic field is uniform and out of the paper. What is the direction of the current flow through the R? A) clockwise B) counterclockwise C) I=0

Example 10 The square loop of wire moves at constant speed through a region of uniform magnetic field B (into the page). The field is zero outside the dashed rectangle. Which graph best represents the emf induced in the square loop as a function of time?      x x x   t = 0 t = t f tftf D tftf A tftf B tftf C

Example 11 A flat circular coil with 100 turns (each loop is identical) has inductance L 1. A second coil, of the same size, shape and current passing through the conductor but with 50 turns, would have inductance: A) 2L 1 B) L 1 C) ½ L 1 D) ¼ L 1