Phys. 155 Lecture 11
Magnetic Torque. Magnetic Field Production
Outline:
Review: Force on a wire.
Magnetic Torque:
= I A B;
| = I A B sin
Problems: Magnetic torque, tilted loop, deflected rod.
Introduction: Electromagnetism.
Magnetic field of a str
Phys. 155 Lecture 12
Magnetic Field Production, Amperes Law,
Magnetic Materials
Outline:
Demonstration: Oersted experiment, Parallel wires.
Problems: Torque, B-field of wires
Magnetic field of a current (circular) loop and of a solenoid.
Problem: Net
Phys. 155 Lecture 10
Force on a Current Carrying Conductor in B Field
Outline:
Review: Force on a moving charge
Velocity Separator E and B field effects compensated
J.J. Thomson experiment to determine the charge/mass ratio
of the electron
Force on a
Phys. 155 Lecture 9
Magnetic Field and force on a moving charge
Outline:
Permanent magnets
Magnetic field concept
Force on a moving charge:
- Expression
- Right hand rule
Work done by force on a moving charge
Circular trajectory motion:
- Centripetal
Part 2: Electric Circuits
Example solutions
Dr. Chijin Xiao
Phys155-part2-Example solutions, Xiao, 2015
1
Plancks constant
=6.63x1034 Js = 4.14x 1015 eVs
Photon energy
=
f (or ) is the frequency of the light
cycles/second (Hertz, Hz)
Wavelength
=
c= 3
Physics
Cutnell & Johnson (9th ed.)
Chapter 19.5, 20.12, 20.13
Pages 579-583, 620-623
Phys155-Pt2-08-circuits with capacitors, C. Xiao, 2015
1
In this section of my lectures we will
be revisiting the key equations for
capacitors.
We will also introduce a
Physics
Cutnell & Johnson (9th ed.)
Chapter 20
Phys155-part2-07-Circuit Analysis II, C. Xiao, 2015
1
When circuits get really complex
methods learned so far will still work,
but they can take a long time to do.
A particularly bad case is using the
Superp
Physics
Chapter 20.6-20.8, 20.10
Pages 606-614, 615-618
Phys155-part2-05-Series and Parallel Circuits, C. Xiao, 2015
1
In this section of lectures we will be
developing the two common types of
resistor arrangements; series and
parallel.
To do this we wil
Physics
Cutnell & Johnson (9th ed.)
Chapter 20.3
Pages 601-603
Phys155-part2-04-Ohms Law, C. Xiao, 2015
1
In this lecture we will be developing
the relationship between voltage,
current and resistance.
Power equations for resistors will also
be developed
Physics
Cutnell & Johnson (9th ed.)
Chapter 20.3
Pages 598-601
Phys155-part2-03-Resistance, C. Xiao, 2015
1
In this lecture we will be developing the
concept of resistance.
To do this we will use as an analogy of
water flowing in a pipe.
Phys155-part2-03-
Part 2: Electric Circuits
Dr. Chijin Xiao
Phys155-part2-01-Voltage, Xiao, 2015
1
B.Sc.,M.Sc. in Physics from University of Science and
Technology of China in Hefei, China
Dr. rer. nat. (Doctor in Natural Science) in Physics
from Ruhr-Universitt Bochum, Ge
Physics
Cutnell & Johnson (9th ed.)
Chapter 20.1, 20.4
Pages 595-597, 601-603
Phys155-part2-02-Current and Power, C. Xiao, 2015
1
Potential difference (voltage) between two
points causes charges to move (last
lecture)
Media through which the charges flow
Current and Power
C. Xiao
Physics
Cutnell & Johnson (9th ed.)
Chapter 20.1, 20.4
Pages 595-597, 601-603
Conductor
Insulator
Semiconductor
Phys155-part2-02-Current and Power, C. Xiao, 2015
Phys155-part2-02-Current and Power, C. Xiao, 2015
P155-part2-02,
Voltage source
C. Xiao
B.Sc.,M.Sc. in Physics from University of Science and
Technology of China in Hefei, China
Part 2: Electric Circuits
Dr. rer. nat. (Doctor in Natural Science) in Physics
from Ruhr-Universitt Bochum, Germany
Dr. Chijin Xiao
Research I
Problems on force Fi from previous exams
Correct answer is (a)
A wire having a mass per unit length of 0.500 g/cm carries a 2.00-A current horizontally to the
south. What are the direction and magnitude of the minimum magnetic field needed to lift this wi
Problems on force Fi from previous exams
A wire having a mass per unit length of 0.500 g/cm carries a 2.00-A current horizontally to the
south. What are the direction and magnitude of the minimum magnetic field needed to lift this wire
vertically upward?
Additional problems for Lectures 3-4.
Torque:
A coil carries a current and experiences a torque due to a magnetic field. The value of
the torque is 80% of the maximum possible. (a) What is the smallest angle between the
magnetic field and the normal to th
Solutions to problems considered in
class
(Lectures 1-2)
Test question:
A proton traveling due west in a region that contains only a magnetic field experiences a vertically upward force (away from the surface of the
earth). What is the direction of the ma
Additional problems for Lectures 5-6.
Lenz:
1. A flexible, circular conducting loop lies in a uniform magnetic field, as shown below.
The loop is pulled on opposite sides by equal forces and stretched until its
enclosed area is essentially zero, as sugges
Solutions to problems considered in
class
(Lectures 3-4)
Solution
Given are B, I, L (length) and m
(mass) of the conductor.
How to determine the angle?
2
Solution for 2 turns loop torque
Magnitude of torque=NIAB=2x10^(-2)A*3.14x1^2m^2*0.5T=3.14x10^(-2) Nm
Solutions to additional problems for Lectures 3-4.
Torque:
A coil carries a current and experiences a torque due to a magnetic field. The value of
the torque is 80% of the maximum possible. (a) What is the smallest angle between the
magnetic field and the
1
Faraday law of induction
Lenzs rule
2
Last time:
Motional emf
Em L V B
DC geneator
3
Example of a problem on motional emf: A bar
accelerates from the rest down the slides of length S.
There is a magnetic field B set downwards. What is
the velocity of th
1
1. Torque on a current-carrying
loop in magnetic field t
2. Production of magnetic field by
currents:
straight line current
2
Current-carrying loop in B field
Sum of the forces is zero, but
the loop experiences rotations
F
F
Tendency of the magnetic for
1
1. Production of magnetic field by currents:
current loop
solenoid
2. Amperes law
3. Magnetic materials
4. Motional emf
2
Summary of previous equations
0 I
| B |
2r
0 I1 I 2
| F |
L
2 d
3
Example of a problem
3
0.500 T
10.0 mA
2
1.00 m
4
1
A 2 turns c
1
Major news:
Force on a currentcarrying conductor in
magnetic field: FI
2
For a particle to be on a circle, the magnetic force Fq must
be directed toward the center of the curvature
3
Review 1
A negatively charged particle moves along circle in B field
4