Fleming’s Left-Hand Rule and the Right-Hand Palm Rule are visual tools used to predict directions in electromagnetic interactions.
Fleming’s Left-Hand Rule applies to electric motors and helps determine the direction of the force (motion) on a current-carrying conductor placed in a magnetic field. By aligning the thumb (force, $F$), first finger (magnetic field, $B$), and second finger (current, $I$) at right angles, one can deduce the force direction.
The Right-Hand Palm Rule serves the same purpose, but might actually be more intuitive, as the fingers would look like parallel vectors in a uniform magnetic field. The thumb points in the direction of the current. The hand will then naturally look like it is exerting a push in the direction of the palm.
I like to joke with my class that both serve the same purpose but one resembles a gun while the other resembles a kungfu move. Which would you prefer?
Side note: The image above is generated using a single prompt with ChatGPT 4o: “draw an image representing fleming’s left hand rule, next to the right-hand palm rule.” I’m impressed by how far AI image generation has come.
Live wire: wire carrying the current at a high voltage from the power source to the electrical appliance.
Neutral wire: wire completing the circuit by carrying current back to the power source, maintaining a low potential close to zero volts.
Earth wire: wire provides a path for electrical current to flow safely into the ground in case of a fault, preventing the appliance’s exterior from becoming live and reducing the risk of electric shock.
Switch: a device that opens and closes the circuit. Connected to the live wire instead of neutral wire so that device does not remain live when current is off.
Fuse: a safety device connected to the live wire and is designed to melt/break, thus creating an open circuit, when the current passing through it exceeds a specified value. Its current rating should just be slightly higher than the normal operating current.
Circuit breaker: a safety device connected to the live wire which switches off the electrical supply when a excessive current flows through it.
Double insulation: two layers of protection to prevent users from coming into contact with live electrical parts, eliminating the need for an earth connection.
Example Scenarios
Fault: You accidentally run over the iron’s cord with a chair, exposing the internal wires. Exposed live wire touches the metal casing.
Protection:
Earth Wire diverts the fault current safely to the ground.
Circuit Breaker detects the sudden surge and cuts off power immediately OR
Fuse in the plug blows to break the circuit.
If the appliance had Double Insulation, the user will not be able to touch the metal casing.
Fault: You plug too many devices into the same extension cord, leading to overloading — the total current drawn exceeds the safe current rating.
Protection:
Fuse in the plug blows to break the circuit.
Circuit Breaker in the consumer unit (distribution board) trips, cutting off power.
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This simulation offers a hands-on and dynamic way to explore the physics of projectile motion with and without air resistance. By adjusting parameters such as launch velocity, angle, and air resistance, users can visualize how these factors affect the shape and reach of a projectile’s trajectory. The app provides real-time changes including motion paths, velocity vectors, and a velocity-time graph showing horizontal and vertical components separately. It also calculates and displays key quantities such as maximum height and range under ideal and non-ideal conditions (based on an arbitrary coefficient of drag.
Through interactive experimentation and visual reinforcement, learners gain a deeper understanding of concepts the effect of air resistance, and the difference between theoretical and real-world motion.
This is suitable for JC1’s topic on projectile motion. It can also be used for Upper Sec, if you change the launch angle to 90 degrees.
Click on the canvas to place the body at your desired location.
Label the Body.
Add Forces:
Click the “Add Force” button.
Click on two bodies that exert the force on each other.
Label the Force.
Using System Schema to Understand Newton’s Third Law
Newton’s Third Law states that when Body A exerts a force on Body B, Body B exerts an equal and opposite force on Body A. While this principle is conceptually simple, many students struggle to apply it consistently across different physical scenarios. The System Schema approach provides a powerful way to visualise and analyse these interactions. It is a representation tool developed by The Modeling Instruction program at Arizona State University (Hinrichs, 2004).
A system schema is a diagram that represents objects (as circles) and interactions (as lines) between them. Instead of focusing on individual forces, a system schema helps students see the relationships between objects before applying force diagrams. This method emphasizes Newton’s Third Law by explicitly showing how forces come in pairs between interacting objects.
To correctly identify action-reaction force pairs, consider the following guidelines:
Forces Act on Different Objects: Each force in the pair acts on a different object. For example, if Body A exerts a force on Body B, then Body B simultaneously exerts an equal and opposite force on Body A.
Forces Are Equal in Magnitude and Opposite in Direction: The magnitudes of the two forces are identical, but their directions are opposite.
Forces Are of the Same Type: Both forces in the pair are of the same nature, such as gravitational, electromagnetic, or contact forces.
The steps to applying System Schema to Newton’s Third Law are as follow:
Identify the bodies in the system – Draw each object as a separate circle.
Represent interactions – Draw lines between bodies to indicate forces they exert on each other (e.g., a box on the ground interacts with Earth through gravitational force).
Label force pairs – Each interaction represents an action-reaction force pair (e.g., a hand pushes a wall; the wall pushes back).
By mapping forces this way, students can easily recognize that forces always act between bodies and in pairs, reinforcing the symmetry of Newton’s Third Law.
One of the most common misconceptions of students is that normal contact force and gravitational force acting on a body are action-reaction pairs because they are equal and opposite in a non-accelerating system. By using the system schema, they can see that the two forces involve interaction with different bodies, e.g. the floor of an elevator for normal contact force, and the Earth for gravitational force.
Understanding motion in physics often involves analyzing displacement, velocity, and acceleration graphs. With the interactive GeoGebra graph at this link, you can dynamically explore how these concepts are connected.
How It Works
This interactive simulation lets you visualize an object’s motion and its corresponding displacement-time, velocity-time, and acceleration-time graphs. You can interact with the model in two key ways:
Adjust Initial Conditions:
Move the dots on the graph to change the starting displacement, velocity, or acceleration.
Observe how these changes influence the overall motion of the object.
Use the Slider to Animate Motion:
Slide through time to see how the object moves along its path.
Watch the displacement vector, velocity vector, and acceleration vector update in real time.
Key Observations
When displacement changes, the velocity and acceleration graphs adjust accordingly.
A constant acceleration results in a straight-line velocity graph and a quadratic displacement graph.
Negative acceleration (deceleration) slows the object down and can cause direction reversals.
If velocity is constant, the displacement graph is linear, and acceleration remains at zero.
Why This is Useful
This GeoGebra tool is perfect for students and educators looking to build intuition about kinematics. Instead of just solving equations, you get a visual and hands-on way to see the relationships between these key motion variables.
Try it out yourself and experiment with different conditions to deepen your understanding of motion!
This week, I conducted a lesson on motion for my IP3 class using a simple yet effective tool: a simulated ticker tape timer. The objective was to help students develop an intuitive understanding of uniform and non-uniform motion by actively engaging in an experiment.
Introduction to the Ticker Tape Timer
To kickstart the lesson, I showed my students a YouTube video that explains how a ticker tape timer works:
This video provided a visual demonstration of how a ticker tape timer marks regular intervals on a moving strip of paper, allowing us to analyze motion quantitatively.
Hands-On Experiment: Simulating a Ticker Tape Timer
After the video, I had students pair up for a hands-on activity. Instead of using an actual ticker tape timer, we simulated the process using paper strips cut from A3-sized sheets. Each pair had one student act as the “moving arm,” responsible for placing dots on the strip, while the other played the role of the “puller,” responsible for pulling the paper strip at different speeds.
To ensure a consistent time interval between each dot, I used a Metronome App that I created:
This app produces a steady rhythm at 120 beats per minute, meaning that the interval between each beep (and consequently each dot) is 0.5 seconds. To improve accuracy, the student acting as the moving arm was instructed to close their eyes and focus solely on the beep.
Step 1: Recording Uniform Motion
In the first trial, the puller was asked to pull the paper at a constant rate. As the paper moved steadily, the moving arm marked dots at regular intervals based on the metronome beat. After completing the trial, students used a ruler to measure the distances between successive dots. Since the time interval was fixed, they could easily calculate the speed of the paper by using:
Step 2: Recording Accelerated Motion
Next, the students switched roles. This time, the new puller was asked to gradually increase the speed of the paper. As expected, the spacing between dots increased progressively, providing a clear visual representation of acceleration. This led to discussions on how motion can be analyzed using dot patterns and how acceleration differs from uniform motion.
Reflections and Key Takeaways
This activity was highly effective in reinforcing key motion concepts. Since we do not have an actual ticker tape machine, it allowed students to engage in a hands-on simulation while visually and physically experience motion rather than just reading about it.
Next Steps
To extend this lesson, I plan to introduce velocity-time graphs and have students plot their measured speeds to analyze changes in motion further. Additionally, incorporating digital tools like video analysis with Tracker software could help reinforce these concepts further.
If you have any feedback or suggestions, feel free to share them in the comments below!
