This slide is the fifth section (last section) of 203PHYS course - Physics 2 for Engineering, Jazan University.

1. 203 PHYS - Physics 2
(for Engineering)
Instructor:
Dr. Sabar Hutagalung ‫د‬.‫هوتاغالونغ‬ ‫سابار‬
Physics Department, Faculty of Science, Jazan University
Jazan, Saudi Arabia
Email: sdhutagalung@gmail.com

2. MAGNETIC FIELDS

3. Main Reference
• Raymond A. Serway & John W. Jewett, Jr., Physics for
Scientists and Engineers with Modern Physics, 9th Edition,
Brooks/Cole, 2014.

4. Ampere’s Law
Ampère’s law, can be stated as follows:
SI unit of B is Weber/m2 (Wb/m2),
called tesla (T). 1 T = 1 Wb/m2
Compasses show the effects of the current in a nearby wire

5. Quiz
Answer:
Ia = 1+5-2 = 4 A
Ib = 1-2 = -1 A
Ic = 1+5 = 6 A
Id = 5-2 = 3A
Therefore,
c > a > d > b
inout

6. Quiz
a = c = d > b = 0
At b = 0 because no current
inside the closed path.
ANSWER:

7. Example 30.5
TheMagneticFieldCreatedbyaLongCurrent-
CarryingWire
For

8. The Magnetic Field of a Solenoid
---------- l -------

9. d d d d d           1 2 3 4
B s = B s B s B s B s
Using Ampere’s law:
along sides 2 and 4
0 along side 3
d 


B s
B
0 0 0Bl   
The Magnetic Field of a Solenoid
If N is the number of turns in the length, l, the
total current through the rectangle is NI.
 B external

10. Quiz
Answer: (c)
If n high, then B higher.

11. Faraday’s Law of Induction
Move toward a loop Move away from the loopStationary

12. Faraday’s Law of Induction
• The emf is directly proportional to the time rate of change of
the magnetic flux through the loop.
• Faraday’s law of induction:
is the magnetic flux through the loop.
If a coil consists of N loops with the same
area and FB is the magnetic flux through
one loop, an emf is induced in every loop:
If q is the angle between the magnetic field
and the normal to the loop:

13. Quiz
Answer: (c)

14. Some Applications of Faraday’s Law
The ground fault circuit interrupter (GFCI) is
an interesting safety device that protects
users of electrical appliances against
electric shock.
The production of sound in an electric guitar. The coil in this case, called
the pickup coil, is placed near the vibrating guitar string, which is made of a
metal that can be magnetized.

15. Example:
Inducing an emf in a Coil
• A coil consists of 200 turns of wire. Each turn is a square of side d
= 18 cm, and a uniform magnetic field directed perpendicular to
the plane of the coil is turned on. If the field changes linearly
from 0 to 0.50 T in 0.80 s, what is the magnitude of the induced
emf in the coil while the field is changing?
Assume total resistance of the coil and the circuit is 2.0 W, then

16. Example:
An ExponentiallyDecayingMagnetic Field
The maximum emf occurs at t = 0,

17. The Chinese Proverb
About Money
With money you can buy a House but not a Home
With money you can buy a Clock but not Time
With money you can buy a Bed but not Sleep
With money you can buy a Book but not Knowledge
With money you can see a Doctor but not Good Health
With money you can buy a Position but not Respect
With money you can buy Blood but not Life
With money you can buy Sex but not Love