Announcements:

1. Announcements: Physics department has arranged for Physics 121 tutoring by Natasha Parikh on Thursdays from 12:00 Noon to 4:00 PM in the Physics Conference room. This is in addition to tutoring provided by CAPE and perhaps some other groups in NJIT.

2. Preparations for Common Exam 1 – LECTURES 1, 2, 3, 4 of material NOTE: Old practice exams may cover MORE or LESS material than THIS YEARS weeks 1-4 of material • First, download the equation sheet and USE THAT SHEET when you are practicing for the exam. Make sure that you know • what EACH equation means • What the different symbols mean • How the equation is used.

3. Preparations for Common Exam 1 – Lectures 1, 2, 3, 4 of material • COMMON exam is ALL MULTIPLE CHOICE questions • typically 14 problems and 2 “extra-credit” problems • Conceptual questions • simple calculation problems (typically one concept being tested) • More complicated problems (several concepts used together) • There WILL be calculus-based problems on the exam. • You should review – • Assigned HW problems • Examples from Class • Recitation problem examples • Old Exams • Other Physics 121 instructors sample exams.

4. Clicker Question #0 When would be a good time for an OPTIONAL review for the common exam? • Thursday Feb 9th @ 10AM • Thursday Feb 9th @ 1PM • Thursday Feb 9th @ 2:30PM • Friday Feb 10th @ 11:30AM • Friday Feb 10th @ 1:00PM

5. Electric Flux

6. Clicker Question #1 Which of the following statements are true about the flux through the various sides of the box below? • Can not answer unless one knows the distribution of charges. • The flux through the left and the right side of the box are both equal. • The flux through the top of the box is zero. • The flux through the bottom of the box is zero because the electric field is zero. • None of the above are true.

7. Clicker Question #2 In HOW MANY of these illustrations is the net flux NOT equal to zero? A) in all, net flux is zero B) only one, C) two D) all but one E) net flux never zero

8. How does the flux depend of the charge?

9. Clicker Question #3 What is the next flux through the shaded blue surface? A) -6 C/εo B) +3C/εo C) -3C/εo D) Zero E) Can not calculate unless given exact shape of blue shaded surface.

10. Clicker Question #4 The total charge on the conducting inner sphere is Q. The total charge on the outer spherical shell (also conducting) is zero. Which of the following statements is false A) The electric field inside of the central sphere is zero. B) The charge on the INSIDE surface of the shell is -Q C) The charge on the OUTSIDE surface of the shell is Q D) The electric field in between the two conductors is non-zero. E) The magnitude of the charge per area σ on the inner and outer surfaces of the shell are equal.

11. Clicker Question #5 Which of the following statements is false? A) The electric field inside of the central sphere is zero. B) The charge on the INSIDE surface of the shell is -Q C) The charge on the OUTSIDE surface of the shell is Q D) The electric field in between the two conductors is measured relative to center of center sphere. E) The electric field in between the two conductors can not be easily calculated between the two conductors using Gauss’s law.