Force Fields Infographic Force Fields
Magnetic Forces Unit Summary
Name: __________________________
Date: ___________________________
Lorentz Force & RHR
The Equation
\( F = qvB \sin\theta \)
Force (N) = Charge (C) × Velocity × Field (T)
Right-Hand Rule (RHR-1):
Thumb: Velocity (v) or Current (I)
Fingers: Magnetic Field (B)
Palm: Magnetic Force (F)
Negative Charge: Force is in opposite direction!
Field Lines
Properties:
Exit North, Enter South
Lines never cross
Density = Strength
Form closed loops
N
S
Dipoles Only
Ferromagnetism
Aligned domains turn materials (Fe, Co, Ni) into permanent magnets.
Motors & Solenoids
Solenoid strength (B):
More
Higher
Soft
Motor Principle
Wire in field + Current = Mechanical Force
\( F = BIL \sin\theta \)
Electrical
Mechanical
Induction
Magnetic Flux (\(\Phi\))
\( \Phi = BA \cos\theta \)
Amount of field "piercing" an area.
Laws of induction:
Faraday: Changing flux creates Induced Voltage (EMF).
Lenz: Direction of current opposes the flux change.
Generators
Mechanical Motion → Magnetic Change → Electricity
Field (B)
Tesla (T)
Flux (\(\Phi\))
Weber (Wb)
EMF (\(\varepsilon\))
Volts (V)
Critical Check
Force = 0 if velocity is parallel to field lines.
Motor Momentum Bellringer Motor Momentum
Unit 05: Magnetic Forces & Fields
Name:
Date:
The Science of Motors
The Lorentz Force is the engine of our motor. When current flows through the wire in a magnetic field, the charges experience a force. The coil acts as an electromagnet , interacting with the permanent magnet to create torque. We strip insulation on only half the wire to "break" the circuit periodically, allowing momentum to carry the coil through its rotation without the fields locking together.
Blueprint: Labeled Diagram
Sketch your motor setup. Label the coil, magnets, and battery.
Component Analysis
Motor Part Purpose in the System Copper Wire Coil Permanent Magnet Battery / Source
Performance Reflection
1. My motor was successful / unsuccessful because...
2. One specific challenge I faced during the assembly was...
3. I noticed that when I adjusted the magnet's distance from the coil...
Connecting to the Unit
Explain how the Right Hand Rule applies to your motor. In which direction was the magnetic force acting on the top of your coil when current was flowing? (Up, Down, Left, or Right).
"Electricity is just organized lightning." — Practice makes progress!
Magnetic Jigsaw Task Cards Magnetic Jigsaw
Review Expert Set A
PHYS-U05-REV
01
Domains
A permanent bar magnet is snapped exactly in half. Describe the magnetic poles of the two resulting pieces. Why does this happen at the atomic level?
Student Response:
02
Lorentz
A proton (\(q = +1.6 \times 10^{-19} \text{ C}\)) moves at \(4.0 \times 10^{6} \text{ m/s}\) perpendicular to a \(0.5 \text{ T}\) magnetic field. Calculate the magnitude of the force.
Show Work & Answer:
03
RHR Pract.
An electron is moving East through a magnetic field directed North . In which direction is the magnetic force acting?
A) UP
B) DOWN
C) SOUTH
D) ZERO
Final Answer:
04
Wire Angle
A wire \(2.0 \text{ m}\) long carries a \(5.0 \text{ A}\) current. If it experiences a force of \(1.5 \text{ N}\) in a field of \(0.3 \text{ T}\), what is the angle \(\theta\)?
Show Work:
Magnetic Jigsaw
Review Expert Set B
PHYS-U05-REV
05
Solenoids
Name three specific modifications you could make to an electromagnet (solenoid) to increase the strength of its magnetic field.
Response:
06
Commutators
In an electric motor, what is the role of the Commutator ? Why is it essential for the motor to complete a full rotation?
Response:
07
Induction
According to Faraday's Law, what must happen to the magnetic flux through a loop of wire in order to induce an EMF?
Response:
08
Lenz's Law
A magnet's North pole is pushed into a stationary coil of wire. What is the direction of the induced magnetic field created by the coil?
Response:
Field Guide Study Resource Magnetic Forces
Unit 05 Field Guide
PHYSICS CORE
Magnetic Fundamentals
Poles: Every magnet has a North (N) and South (S) pole. Like poles repel; opposite poles attract.Domains: Clusters of atoms with aligned magnetic fields. Magnetization occurs when these align.Magnetic Fields (B): Lines exit North and enter South. Density represents strength.
Electromagnetism
Moving Charges: Current produces a magnetic field (\(B\)). Use the Right Hand Rule .Solenoids: Coils of wire. Strength increases with more current (\(I\)), more turns (\(N\)), or an iron core.Induction: Changing magnetic flux induces a current in a conductor.
Essential Calculations
Magnetic Force on Wire
\[F_{mag} = B \cdot I \cdot L\]
B (Tesla), I (Amps), L (Meters)
Solenoid Proportionality
\[B \propto \frac{N \cdot I}{L}\]
N (Turns), I (Current), L (Length)
Right Hand Rule Guide
Thumb: Direction of Current (\(I\))
Fingers: Curl to show Direction of Field (\(B\))
Used for straight wires and loops.
Generators
Convert kinetic energy to electricity via induction.
Quick Check Practice
1. If you triple the number of turns in a solenoid while keeping the current and length the same, what happens to the magnetic field strength?
2. A 2-meter wire carries 5A of current in a 0.5T field. Calculate the magnetic force.
DCA Physics Unit 05 - Magnetism Mastery Study Guide
Motor Momentum Key Motor Momentum
Teacher Answer Key & Facilitation Guide
UNIT 05: MAGNETIC FORCES
Component Analysis Key
Motor Part Scientific Purpose Copper Wire Coil Acts as the armature/electromagnet . When current flows through the loops, it generates a temporary magnetic field. This field interacts with the permanent magnet to produce torque. Permanent Magnet Provides a constant external magnetic field . This field is essential for the Lorentz force to occur; without a stationary field, the temporary field of the coil would have nothing to push against. Battery / Source Provides the voltage and electric current necessary to power the electromagnet. It converts chemical energy into electrical energy to drive the charges through the circuit.
Common Student Troubleshooting (Reflections 1-3)
Why it might fail:
Insulation: Stripping the wire incorrectly (stripping all of it vs. only half) prevents the circuit from "pulsing" to maintain rotation.Balance: If the coil is lopsided, gravity will overcome the magnetic torque.Continuity: Poor contact between the supports and the coil ends.
Adjusting Distance:
Magnetic field strength (B) follows the inverse square law. Moving the magnet closer increases the magnetic force (F = BIL), leading to faster rotation. Moving it too close may cause the coil to jump or stick.
Connecting to the Unit: RHR Application
Students should use the Right Hand Rule for Force on a Wire :
Index Finger
Current Direction (I)
Middle Finger
Magnetic Field (B)
Thumb
Magnetic Force (F)
Sample Explanation: "If current flows from right to left across the top and the magnetic field is pointing UP from a magnet placed below, the force on the top segment of the coil will be OUT of the page (towards the student), causing the top to push toward them and the coil to spin."
Quick Grading Rubric
DIAGRAM
Labeled & Clear
TABLE
Scientifically Accurate
REFLECTION
Critically Evaluated
RHR
Correct Application
Magnetic Jigsaw Answer Key Jigsaw Answer Key
Teacher Facilitation Guide
PHYS-U05-KEY
CARD 01 Domains
Both pieces become complete magnets with North and South poles.
Magnetism is atomic. Breaking doesn't isolate poles; it creates two smaller sets of aligned domains.
CARD 02 Lorentz Force
\( F = 3.2 \times 10^{-13} \text{ N} \)
\( F = q \cdot v \cdot B \)
CARD 03 RHR Practice
Answer: B) DOWN
RHR gives "Up" for (+). Since electrons are negative , direction reverses to Down .
CARD 04 Wire Angle
\( \theta = 30^\circ \)
\( F = I \cdot L \cdot B \cdot \sin(\theta) \)
CARD 05 Solenoids
Increase current (I).
Increase coils (N).
Add ferromagnetic core.
CARD 06 Commutators
Reverses current every 180°. Keeps torque in same direction for continuous rotation.
CARD 07 Induction
Magnetic flux must change over time.
\( \text{EMF} = -N \cdot \frac{\Delta \Phi}{\Delta t} \)
CARD 08 Lenz's Law
Induced field will Oppose the change (repulsive North pole).
Jigsaw Mastery
Assign students to "Base Groups" of 4. Then, regroup into "Expert Groups" where they master two cards. Experts return to teach their home group. Each student must fill their own task set.
Common Pitfalls
RHR Flip: Remind students that RHR assumes (+) charge. Flip for electrons.Flux Change: Emphasize that a static field induces zero current. Force Fields Worksheet Force Fields Worksheet
Magnetic Forces Unit Assessment
Name: __________________________
Date: ___________________________
Instructions: Refer to your infographic. Show all work for calculations, including equations and units. Use \( g = 9.8 \, \text{m/s}^2 \) and \( \pi \approx 3.14 \).
1
Lorentz Force & RHR
1. An electron moves eastward at \( 2.5 \times 10^6 \, \text{m/s} \) through a magnetic field of \( 0.15 \, \text{T} \) directed vertically upward. Determine the direction of the magnetic force on the electron.
North
South
Up
Down
2. Calculate the magnitude of the force on a \( +5.0 \times 10^{-6} \, \text{C} \) charge moving at \( 4.0 \times 10^5 \, \text{m/s} \) perpendicular to a \( 0.80 \, \text{T} \) magnetic field.
2
Motors & Solenoids
3. A \( 20 \, \text{cm} \) wire carries \( 4.5 \, \text{A} \) of current. It is in a \( 0.25 \, \text{T} \) field at \( 30^\circ \) to the lines. Calculate the magnetic force on the wire.
4. Which changes increase electromagnet strength? (Select all that apply)
More wire loops
Plastic core
Lower current
Higher voltage
3
Induction & Flux
5. A circular loop (\( r = 0.10 \, \text{m} \)) is in a magnetic field that changes from \( 0.5 \, \text{T} \) to \( 0.1 \, \text{T} \) in \( 2.0 \, \text{s} \). Calculate the induced EMF in the loop. (\( A = \pi r^2 \))
Lenz's Law Challenge
A bar magnet is dropped North-pole-first through a stationary coil. Describe the induced current direction as it enters and leaves the coil. Explain using Lenz's Law.
End of Worksheet • Magnetic Mastery
Mastery Mock Exam Unit 05 Mastery Check
Magnetic Forces & Fields
Name:
Date:
Read each question carefully. For multiple-choice questions, select the best possible answer. For multi-select questions, follow the instructions provided.
A standard iron nail is not normally a magnet. However, when it is brought near a powerful neodymium magnet, it becomes capable of picking up paperclips. What physical change occurred within the nail?
The nail’s atomic structure changed from iron to a magnetic isotope.
Magnetic domains within the iron aligned in the direction of the external field.
Electric current began to flow in a closed loop through the nail's surface.
The nail absorbed magnetic particles from the neodymium magnet via contact.
A student is building a simple generator for a science fair. Which of the following modifications would increase the amount of induced electric current produced by the generator?
Replacing the copper wire with a thicker, non-conductive plastic wire.
Rotating the coil slower within the magnetic field.
Using a stronger permanent magnet to increase the magnetic flux change.
Removing half of the turns of wire from the rotating coil.
Two bar magnets are placed near each other. Magnet A has its North pole facing Magnet B’s South pole. Magnet B is then flipped so its North pole faces Magnet A's North pole. What describes the interaction before and after the flip?
Before: Attraction; After: Repulsion
Before: Repulsion; After: Attraction
Before: Attraction; After: No force
Before: Repulsion; After: No force
Which of the following actions would increase the magnetic field strength of a solenoid? (Select TWO)
Decreasing the number of turns of wire while keeping the length constant.
Inserting an iron core into the center of the coil.
Increasing the electric current flowing through the wire.
Using a non-magnetic plastic core instead of air.
A wire with a length of 2.5 meters carries a current of 4.0 Amps. It is placed in a uniform magnetic field of 0.8 Tesla. Calculate the magnitude of the magnetic force exerted on the wire.
Final Answer:
Feature Solenoid X Solenoid Y
Force Fields Answer Key Force Fields Answer Key
Teacher Reference • Solutions
1
Lorentz Force & RHR
1. Electron Direction
Correct Answer: South South .
2. Lorentz Calculation
F = qvB sin(θ)Answer: 1.6 N
2
Motors & Solenoids
3. Force on Wire
F = BIL sin(θ)Answer: 0.11 N
4. Electromagnet Strength
Correct Answers:
3
Induction & Flux
5. Induced EMF
A = πr^2 = 3.14 × (0.10 m)^2 = 0.0314 m^2Answer: 6.3 x 10^-3 V (or 6.3 mV)
6. Lenz's Law Challenge
As North pole enters: Downward flux is increasing. Coil induces upward field to oppose change. Current is Counter-Clockwise (viewed from above).As North pole leaves: Downward flux is decreasing. Coil induces downward field to maintain flux. Current reverses to Clockwise .
Teacher Answer Key • Magnetic Mastery
Mock Exam Key Answer Key
Unit 05 Mastery Check: Magnetic Forces
Teacher Reference
1 Correct Answer: B
Explanation: When a ferromagnetic material (like iron) is exposed to an external magnetic field, the randomized magnetic domains within the material align with the field, causing the material to become magnetized.
2 Correct Answer: C
Explanation: Induced current depends on the rate of change of magnetic flux. A stronger permanent magnet increases the total magnetic field density, creating a greater change in flux as the coil rotates.
3 Correct Answer: A
Explanation: Initially, opposite poles (N and S) were facing each other, causing attraction . After the flip, like poles (N and N) were facing each other, resulting in repulsion .
4 Correct Answers: Inserting an iron core & Increasing current
Explanation: The magnetic field strength of a solenoid (\(B\)) is directly proportional to the current (\(I\)) and the number of turns (\(N\)). Adding a ferromagnetic iron core significantly enhances the field density.
5 Correct Answer: 8.0 N
Step-by-Step Solution:
Identify Knowns: \(L = 2.5\,m\), \(I = 4.0\,A\), \(B = 0.8\,T\)
Apply Force Formula: \(F = B \cdot I \cdot L\)
Substitute: \(F = (0.8\,T) \cdot (4.0\,A) \cdot (2.5\,m)\)
Calculate: \(F = (0.8) \cdot (10.0) = 8.0\,N\)
6 Correct Answer: B
Explanation: Solenoid strength is proportional to \(N \cdot I\) (Turns \(\times\) Current).
Solenoid X: \(200 \times 1.0 = 200 \text{ factor}\)
Solenoid Y: \(100 \times 4.0 = 400 \text{ factor}\)
Therefore, Solenoid Y is twice as strong as Solenoid X.
Unit 05 Magnetic Forces - Mastery Exam Key
Field Force Lab Activity Guide Jumpstart Series
Field Force Lab
Fast-Track Review of Unit 05 Concepts
Est. Time 45 MIN
Name:
Date:
STATION 1: The Domain Map
Procedure: Place a bar magnet under a sheet of cardstock. Sprinkle iron filings slowly over the paper. Tap the edge of the paper gently.
Sketch Your Observations Below:
Where is the field strongest? How do the filings show this?
Key Concept: Domains
Magnets work because regions of alignment called domains all point in the same direction. When randomized, magnetism is lost!
STATION 2: Coil Power
Procedure: Wrap wire around a nail. Connect to a battery. Count how many paperclips it lifts. Repeat with double the number of wraps.
Setup # of Turns (N) Paperclips Lifted Trial A 10 turns Trial B 20 turns
What is the relationship between the number of turns (N) and magnetic force?
STATION 3: The Spark
Procedure: Connect a coil to a galvanometer. Move a bar magnet in and out of the coil. Observe the needle deflection.
1. What happens when the magnet is stationary inside the coil?
2. What happens when you move the magnet faster ?
Induction
Current requires change —a changing magnetic field through a conductor induces current. This is how power plants work!
The Mastery Connection
If we used a 9V battery instead of a 1.5V battery (increasing the current, I), what would happen to the solenoid's force? Use the relationship B is proportional to N times I to explain.
Magnetic Mastery Jumpstart • Lab 05-A
Field Force Lab Teacher Guide Teacher Facilitation Guide
Field Force Lab: Unit 05 Catch-Up Review
Unit 05: Magnetism
Station Setup & Expected Results
Station 1: The Domain Map
Setup: Easy
Materials: Bar magnets, iron filings, white cardstock.
Outcome: Filings should concentrate at the poles, showing that the magnetic field (B) is densest where the force is strongest.
Concept: Emphasize that magnetism is about the alignment of domains , not "magic" particles.
Station 2: Coil Power (Solenoids)
Setup: Moderate
Materials: D-cell battery, copper wire, iron nail, paperclips.
Outcome: 20 turns will lift more clips than 10. This visually proves that B is proportional to the number of turns (N) .
Safety: Disconnect batteries between trials to prevent overheating.
Station 3: The Spark (Induction)
Setup: Moderate
Materials: Pre-coiled solenoid, bar magnet, galvanometer.
Outcome: Only motion causes deflection. Speed increases current. This is Faraday's Law of Induction in action.
Tip: Ensure wire connections are secure. If the needle is shaky, check for nearby electrical interference.
Synthesis Answer Key
A 9V battery has a higher potential difference than a 1.5V battery.
Since Current (I) = Voltage (V) / Resistance (R) , increasing voltage increases the current flowing through the solenoid.
Because Magnetic Field (B) is proportional to Current (I) , the electromagnet will become significantly stronger.
TEACHER RESOURCE • UNIT 05 MAGNETISM REVIEW
Magnetic Mastery Slides Magnetic Mastery
Unit 05: Forces & Fields
Mission Objectives
1
Understand how magnetic domains create permanent magnetism.
2
Apply the Right Hand Rule to determine field directions.
3
Calculate magnetic force on current-carrying wires.
4
Explain electromagnetic induction in generators.
The Power of Poles
FUNDAMENTALS
Magnetic Poles
Every magnet has a North (N) and South (S) pole. They never come alone—break a magnet, and you get two smaller magnets!
Like Poles
REPEL
Opposite
ATTRACT
N
S
Inside the Magnet: Domains
Unmagnetized Iron
Magnetic domains are clusters of atoms. When they point in random directions , their fields cancel out.
Magnetized Iron
When domains align in the same direction , the object becomes a magnet. This happens near strong fields.
Electricity & Magnetism
In 1820, Hans Christian Ørsted discovered that an electric current creates a magnetic field .
The Core Rule
"Moving charges are the source of all magnetic fields."
Electromagnetism
The physical interaction between electric fields and magnetic fields.
The Right Hand Rule (RHR)
THUMB = CURRENT (I)
FINGERS = FIELD (B)
Step 1
Point your thumb in the direction of the current (\(I\)).
Step 2
Your fingers curl in the direction of the magnetic field (\(B\)).
Always use your right hand , even if you are left-handed!
Solenoids: Built Magnets
Increase Current
More amps (\(I\)) = More strength.
Increase Turns
More loops (\(N\)) = More strength.
Add a Core
An Iron Core concentrates the field.
B ∝ (N ⋅ I) / L
Strength is proportional to turns & current, inversely to length.
Magnetic Mastery Slides Magnetic Mastery
Unit 05: Forces & Fields
Mission Objectives
1
Understand how magnetic domains create permanent magnetism.
2
Apply the Right Hand Rule to determine field directions.
3
Calculate magnetic force on current-carrying wires.
4
Explain electromagnetic induction in generators.
The Power of Poles
FUNDAMENTALS
Magnetic Poles
Every magnet has a North (N) and South (S) pole. Like poles repel; opposite poles attract.
Key Fact: They always come in pairs. Break a magnet, and you have two new magnets!
N
S
Inside the Magnet: Domains
Unmagnetized Iron
Magnetic domains are clusters of atoms. When they point in random directions , their fields cancel out.
Magnetized Iron
When domains align in the same direction , the object becomes a magnet. This is usually forced by an external field.
Electricity meets Magnetism
Current flowing through a conductor produces a magnetic field in the space around it.
The Rule:
Moving charges create fields.
Ørsted's Discovery
The Right Hand Rule
Thumb = Current (I)
Fingers = Field (B)
1. Point your thumb in the direction of the Current (I) .
2. Your fingers curl in the direction of the Magnetic Field (B) .
Solenoids: Electromagnets
Higher Current (I)
More amps flowing = Stronger field.
More Turns (N)
Each loop adds to the total force.
Iron Core
Adding iron concentrates the field density.
B ∝ (N x I) / L
The Calculation
F = B x I x L
B
Field (Teslas)
I
Current (Amps)
L
Length (m)
Generating Power
Electricity requires change .
