1 of 39

Physics 1C Midterm 1 Review Session

Sigma Pi Sigma

2 of 39

Key Topics

​

  • Magnetic Field and Magnetic Forces
  • Sources of Magnetic Field
  • Electromagnetic Induction, Faraday’s Law
  • Maxwell’s Equations
  • Inductance
  • RC/ LC / RL Circuits
  • Alternating Current (AC Circuits)

​

Sigma Pi Sigma

2

3 of 39

Magnetic Field and Magnetic Forces

​

Sigma Pi Sigma

3

4 of 39

Magnetic Field and Magnetic Forces

​

Sigma Pi Sigma

4

5 of 39

Magnetic Field and Magnetic Forces

​

Sigma Pi Sigma

5

6 of 39

Sources of Magnetic Field

​

​

Sigma Pi Sigma

6

7 of 39

Sources of Magnetic Field

​

​

Sigma Pi Sigma

7

8 of 39

Sources of Magnetic Field

​

​

Sigma Pi Sigma

8

9 of 39

Sources of Magnetic Field

​

​

Sigma Pi Sigma

9

10 of 39

Electromagnetic Induction

Sigma Pi Sigma

10

11 of 39

Electromagnetic Induction

Sigma Pi Sigma

11

12 of 39

Faraday’s Law

Sigma Pi Sigma

12

13 of 39

Inductance

​

​

Sigma Pi Sigma

13

14 of 39

Inductance

​

​

Sigma Pi Sigma

14

15 of 39

Alternating Current

​

Sigma Pi Sigma

15

16 of 39

Practice Problems

17 of 39

Practice Problem 1:

Sigma Pi Sigma

A square loop of wire with side length a carries a current I1. The center of the loop is located a distance d from an infinite wire carrying a current I2. The infinite wire and the loop are in the same plane; two sides of the square loop are parallel to the wire and two are perpendicular as shown.

  1. What is the magnitude of the magnetic force exerted by the straight wire to the AC segment of the wire loop? Direction?
  2. What is the magnitude of the magnetic force exerted by the straight wire to the BD segment of the wire loop? Direction?
  3. What is the total net magnetic force on the wire loop? Direction?

17

18 of 39

Practice Problem 1:

Sigma Pi Sigma

a. What is the magnitude of the magnetic force exerted by the straight wire to the AC segment of the wire loop? Direction?

Solution:

18

19 of 39

Practice Problem 1:

Sigma Pi Sigma

b. What is the magnitude of the magnetic force exerted by the straight wire to the BD segment of the wire loop? Direction?

​

Solution:

19

20 of 39

Practice Problem 1:

Sigma Pi Sigma

c. What is the total net magnetic force on the wire loop? Direction?

Solution:

20

21 of 39

Any questions on

Problem 1?

Sigma Pi Sigma

21

22 of 39

Practice Problem 2:

Sigma Pi Sigma

2. Assume you have a spool of 22-gauge copper wire, which has a diameter of 0.6426 mm, and a thick “20d” nail, which has a diameter of 5.15 mm. The copper wire is coated with a thin insulator, usually made of plastic but called “enamel”, of negligible thickness. The nail is made out of steel with a relative permeability Km = 1.3 x 103.

​

  1. How many times can you tightly wrap this wire around the nail without overlapping to form a solenoid with a length of 8 cm?
  2. Estimate the inductance of this solenoid, assuming the magnetic field inside is constant.
  3. If a current of 5.0 A flows through the wire wound around the nail, how much magnetic energy will be stored inside?

​

​

​

22

23 of 39

Practice Problem 2:

Sigma Pi Sigma

  1. How many times can you tightly wrap this wire around the nail without overlapping to form a solenoid with a length of 8 cm?

​

Solution:

23

24 of 39

Practice Problem 2:

Sigma Pi Sigma

b. Estimate the inductance of this solenoid, assuming the magnetic field inside is constant.

Solution:

24

25 of 39

Practice Problem 2:

Sigma Pi Sigma

c. If a current of 5.0 A flows through the wire wound around the nail, how much magnetic energy will be stored inside?

​

Solution:

25

26 of 39

Any questions on

Problem 2?

Sigma Pi Sigma

26

27 of 39

Practice Problem 3:

Sigma Pi Sigma

3. An electron moving in vacuum with a velocity enters a region of space where there is a uniform electric field and a uniform magnetic field. The magnetic field is given by . The electron travels through the region at constant velocity.

​

  1. What is the algebraic formula for the electric field vector E in the region?
  2. What is the numeric answer for the electric field vector E in the region?

27

28 of 39

Problem 3 Solution:

Sigma Pi Sigma

  1. What is the algebraic formula for the electric field vector E in the region?

Solution:

28

29 of 39

Problem 3 Solution:

Sigma Pi Sigma

b. What is the numeric answer for the electric field vector E in the region?

Solution:

29

30 of 39

Any questions on

Problem 3?

Sigma Pi Sigma

30

31 of 39

Practice Problem 4:

Sigma Pi Sigma

In the figure below, the magnetic flux through the loop perpendicular to the plane of the coil and directed into the paper is varying according to the relation:

�Where Φm is milli-webers, and t is in seconds.

​

  1. What is the magnitude of the EMF induced in the loop when t = 3.0 sec?
  2. What is the direction of the current through resistor R at that time?

31

32 of 39

Practice Problem 4:

Sigma Pi Sigma

  1. What is the magnitude of the EMF induced in the loop when t = 3.0 sec?

​

Solution:

32

33 of 39

Practice Problem 4:

Sigma Pi Sigma

​

b. What is the direction of the current through resistor R at that time?

​

​

Solution:

33

34 of 39

Any questions on

Problem 4?

Sigma Pi Sigma

34

35 of 39

Extra Problem

35

36 of 39

Extra Tips:

  • Always write down something! Even if you don’t know how to get to the answer oftentimes you can get points for just writing something down.
  • Review practice midterms & previous midterms.
  • Relax, you’ve got this!
  • For numerical problems, you can often get near full marks for writing a solution in terms of variables. If you run out of time, write down variable solutions and use those
  • If you fail to solve the first part of a problem, it is a good strategy to assume an answer with a best guess, and use that guess for future problems

Sigma Pi Sigma

36

37 of 39

Questions?

Sigma Pi Sigma

37

38 of 39

Slides:

Sigma Pi Sigma

38

39 of 39

Good luck, you’ve got this!