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Credits

Fu-Kwun Hwang - Dept. of Physics, National Taiwan Normal Univ.; lookang (This email address is being protected from spambots. You need JavaScript enabled to view it.)

Briefing Document: Direct Current Motor Simulation

1. Overview

This document summarizes key information regarding a 3D WebGL JavaScript HTML5 applet simulation model of a Direct Current (DC) motor, created by Fu-Kwun Hwang and Loo Kang Wee. This simulation is hosted on the Open Educational Resources / Open Source Physics @ Singapore website and is intended for educational purposes. The simulation allows users to explore the principles of DC motor operation through an interactive virtual lab.

2. Main Themes and Concepts

Electromagnetism and Motor Operation: The core concept revolves around the principle that a current-carrying coil within a magnetic field experiences a turning effect due to the magnetic force. This force is the basis of how electric motors convert electrical energy into mechanical energy.
"Electric motors turn electricity into motion by exploiting electromagnetic induction. A current-carrying loop that is placed in a magnetic field experiences a turning effect."
Fleming's Left-Hand Rule: The simulation is designed to help students understand and apply Fleming’s left-hand rule to deduce the direction of the force on a current-carrying wire within a magnetic field.
"(j) deduce the relative directions of force, field and current when any two of these quantities are at right angles to each other using Fleming's left-hand rule"
Torque and Rotation: The turning effect is not just a force, but a torque (rotational force) that is responsible for the coil's rotation. The simulation allows users to explore how different factors affect this torque.
"Taking moments about the axle conveniently, reveals a resultant torque T = FmagADcosθ acts on the coil loop."
Split-Ring Commutator: A key component of a DC motor is the split-ring commutator. The simulation emphasizes its role in reversing the current direction in the coil every half cycle, ensuring continuous unidirectional rotation.
"The purpose of the commutator is to reverses the direction of the current in the loop ABCD for every half a cycle."
Factors Affecting Motor Strength: The simulation highlights how the turning effect can be increased by:
Increasing the number of turns on the coil.
Increasing the current.
Increasing the strength of the external magnetic field.
"Explain how a current-carrying coil in a magnetic field experiences a turning effect and that the effect is increased by increasing (i) the number of turns on the coil, (ii) the current (iii) increasing the magnitude of the external Bz field"

3. Key Ideas and Facts

Simulation Structure: The simulation uses a 3D WebGL interface, making it accessible on various platforms including computers, tablets, and smartphones. It's designed with EasyJavaScriptSimulation.
Components of a DC Motor: The simulation clearly illustrates the main parts:
Armature/Rotor/Coil: The rotating coil of wire, which acts as an electromagnet.
"The armature, carrying current provided by the battery, is an electromagnet, because a current-carrying wire generates a magnetic field"
Stator: The external magnet that provides the magnetic field.
"The motor features a external magnet (called the stator because it’s fixed in place)"
Split-Ring Commutator: The device that reverses current direction.
"A swing back and fro motion (maybe θ = 90o increase to 270o and decrease back to 90o) is all you would get out of this motor if it weren't for the split-ring commutator"
Brushes: The components that make contact with the commutator to pass current into the rotating coil.
"The split-ring commutator allows electricity flows from the positive terminal of the battery through the circuit, passes through a copper brush [rectangle black boxes] to the commutator, then to the armature."
Functionality of Split-Ring: Without the split-ring commutator, the motor would only oscillate rather than rotate continuously. The commutator reverses the current direction at the appropriate moment to ensure a constant rotational force is maintained.
Interplay of Forces: The magnetic force acts on the current-carrying wires within the magnetic field, resulting in a torque that causes the coil to spin.
Reversible Process (Motor/Generator): The document highlights the principle that the same device can function as either a motor (converting electrical energy to mechanical) or a generator (converting mechanical energy to electrical).
AC and DC Generators: It explains how a simple spinning coil in a magnetic field produces alternating current (AC), while a split-ring commutator allows the production of direct current (DC) in a generator.
"Spinning a loop in a magnetic field at a constant rate is an easy way to generate sinusoidally oscillating voltage...in other words, to generate AC electricity. To generate DC electricity, use the same kind of split-ring commutator used in a DC motor to ensure the polarity of the voltage is always the same."

4. Learning Objectives

The simulation model aims to help students:

Understand the relationship between current, magnetic field, and force (Fleming’s left-hand rule).
Explain how a current-carrying coil in a magnetic field experiences a turning effect.
Explain the function of the split-ring commutator in a DC motor.
Identify the various components of a DC motor.
Understand the basic principle of a generator.
Explain how the magnitude of the external magnetic field, number of turns and current affect turning effect.

5. Practical Applications

Exercises: The provided document includes multiple exercises that are meant to be used alongside the simulation to solidify a user's understanding of the principles involved.
Advanced Learner Component: The model even offers an option for advanced learners to remix the model and share their new version with the community.
Teacher Resources: The resource provides various links to videos, lesson plans and other supplementary materials which allow teachers to integrate this material into their teaching.

6. Supplementary Information

Credits: The simulation was created by Fu-Kwun Hwang and Loo Kang Wee.
Related Links: The document provides links to various supplementary resources, including:
Links to app store downloads for the DC Motor simulator.
YouTube video tutorials explaining the concept of DC motors.
Links to educational resources and lesson plans.
Links to other related simulations on the website.

7. Conclusion

The Direct Current Motor simulation is a valuable educational tool that allows students to actively explore and understand the fundamental principles of DC motor operation. The interactive nature of the simulation, coupled with the accompanying resources, provides a holistic learning experience.

This briefing document should provide a comprehensive overview of the provided source material. Let me know if you need any more clarification or further analysis.

Direct Current Motor Study Guide

Quiz

Instructions: Answer the following questions in 2-3 sentences each.

According to the text, what is the primary function of a DC motor?
What are the two main components of a DC motor, as described in the text?
How does the interaction of magnetic fields and moving charged particles lead to rotation in a DC motor?
Explain the role of the split-ring commutator in a DC motor.
What effect does increasing the number of turns on the coil have on the turning effect in a DC motor?
Describe how the direction of the magnetic field (Bz) is determined.
How does the text explain the reversal of current in the coil?
What happens to the coil's motion if the split-ring commutator were not present?
How is the armature described?
How can a device that is a DC motor also function as a generator?

Quiz Answer Key

The primary function of a DC motor is to transform electrical energy into mechanical energy, producing motion by using the interaction between a current-carrying coil and a magnetic field. This conversion is a key principle of the motor's operation.
The two main components of a DC motor, as described in the text, are a stator, which includes an external magnet fixed in place, and an armature (rotor), which is a turning coil of wire that carries the current.
The interaction of magnetic fields and moving charged particles (electrons in the current) results in a magnetic force that creates torque. This torque causes the armature to spin, turning electrical energy into mechanical energy.
The split-ring commutator reverses the direction of the current in the coil every half cycle. This reversal ensures that the torque on the coil continues in the same direction, allowing continuous rotation.
Increasing the number of turns on the coil increases the turning effect in a DC motor because it amplifies the force created by the interaction of current and the magnetic field. Each turn contributes to the overall torque.
The direction of the magnetic field (Bz) is determined by the slider in the simulation. If Bz is positive, it's vertically up. If you vary the slider until Bz is negative, it means the direction of the magnetic field is pointing down.
The reversal of current in the coil occurs when the split-ring commutator changes contact with the brushes as the coil rotates. This action reverses the current's direction, causing a change in the force on the coil's sides.
Without the split-ring commutator, the coil would only swing back and forth, not rotating continuously. The current in the coil would only cause it to move a half turn, and without the reversal it would then just swing in reverse.
The armature is described as a turning coil of wire that carries the current and functions as an electromagnet within the motor. Its rotation is driven by magnetic forces and is where the mechanical motion originates.
A device that is a DC motor can also function as a generator because they are essentially the same device in reverse. Instead of using current to generate motion, a generator is driven by motion to create electrical current.

Essay Questions

Instructions: Answer the following essay questions using your understanding of the source material.

Analyze the significance of the split-ring commutator in the functionality of a DC motor. Detail the step-by-step process and discuss its role in maintaining continuous rotation, and explain what would happen if it were not present.
Explain how the concept of torque is applied in the context of a DC motor, addressing how the forces on different sides of the coil lead to the motor's rotation. How does the magnitude of the external magnetic field (Bz) and the current influence the torque experienced by the coil?
Discuss the relationship between the structure of a DC motor and the principles of electromagnetism. Specifically, relate the functioning of a current-carrying coil in a magnetic field to the generation of motion, and address how Fleming's left-hand rule can be applied to identify force direction.
Compare and contrast the operation of a DC motor and a generator, as described in the text. Include an explanation of how both devices utilize the relationship between electricity and magnetism and why a split-ring commutator is needed in each.
The provided document details a variety of simulation models and experiments. How does the use of interactive simulations and virtual labs, such as the model described, enhance the understanding of DC motor principles for students and how do these simulations improve on traditional physics teaching methods?

Glossary of Key Terms

Armature: The rotating coil of wire in a DC motor that carries the electric current, also known as the rotor or coil. Commutator (Split-Ring): A mechanical device consisting of a split ring that reverses the current direction in the coil every half revolution to maintain consistent torque in a DC motor. Current: The flow of electric charge, measured in amperes (A). In a DC motor, it refers to the movement of electrons through the wire of the coil. Electromagnet: A magnet created by the passage of an electric current through a conductor, like a wire, and the armature in a DC motor behaves like an electromagnet when current flows through it. Electromagnetic Induction: The process of generating an electric current or voltage in a conductor by changing the magnetic field around it. This is key to the way both motors and generators function. Fleming's Left-Hand Rule: A mnemonic used to determine the direction of force on a current-carrying conductor in a magnetic field. The thumb, forefinger, and middle finger, held mutually perpendicular, represent the direction of force, magnetic field, and current, respectively. Magnetic Field (Bz): A region in space where a magnetic force can be detected. In a DC motor, it is the magnetic field created by the external magnets, which interacts with the field generated by the coil. Stator: The stationary part of a DC motor, which includes the external magnet or magnets. Torque: A rotational force that causes an object to rotate around an axis. In a DC motor, torque results from the interaction between the current in the coil and the magnetic field.

Apps

Cover art https://play.google.com/store/apps/details?id=com.ionicframework.dcmotorapp835145&hl=en

https://itunes.apple.com/us/app/dc-motor-3d-simulator/id1162611119?ls=1&mt=8

Sample Learning Goals

O level Syllabus

This helps students learn
explain how a current-carrying coil in a magnetic field experiences a turning effect and that the effect is increased by increasing
(i) the number of turns on the coil,
(ii) the current
discuss how this turning effect is used in the action of an electric motor
describe the action of a split-ring commutator in a two-pole, single-coil motor and the effect of winding the coil on to a soft-iron cylinder

UPPER SEC SCIENCE PHYSICS (EXP/5NA) (2013) (2013)

(j) deduce the relative directions of force, field and current when any two of these quantities are at right angles to each other using Fleming's left-hand rule

(k) explain how a current-carrying coil in a magnetic field experiences a turning effect (recall of structure of an electric motor is not required)

Exercises:

The external magnetic field Bz can be varied using the slider Bz. When Bz is positive, it is in the direction vertically up. Vary Bz until it is negative, what is the direction of the Bz then?
The current comes from the battery higher potential end and travels in a wire forming a closed circuit and travels back to the lower potential end of the battery. When θ = 0o current flows from the battery higher potential end, to the top brush, to the RED split ring, through the coil loop in order ABCD, back to BLUE split ring, bottom brush and lower potential end of the battery. What is the direction of the current flow in wire AB? What is the direction of the current flow in wire CD? using Fleming's left-hand rule, deduce the relative directions of force acting on i) AB ii) CD iii) BC iv) DA. hint: note that Fmag = I*B*L*sin(I&B) may be useful.
By taking moments about the axle PQ, consider the forces on AB and CD, deduce the direction of the torque and the motion if the coil loop was initially at rest (ω = 0 deg/s). Select the suitable sliders of your choice and verify your hypothesis for 2 angles. Discuss with your partner what you have discovered. Ask your teacher if there are any problem/issues faced using this virtual lab.
Explain and show the equations involving T ( in earlier part of question), why the forces on wire BC and DA did not contribute to the calculation of rotating torque about axle PQ?
By considering the forces in the x direction for wire BC and DA, suggest what can happen to the coil loop if the forces are large enough. Suggest why it does not happen in terms of the properties of the wires in the coil loop.
Explain how a current-carrying coil in a magnetic field experiences a turning effect and that the effect is increased by increasing (i) the number of turns on the coil, (ii) the current (iii) increasing the magnitude of the external Bz field
After conducting some inquiry learning on the virtual DC motor model discuss how this turning effect is used in allowing the coil loop to rotate. You may right-click within a plot, and select "Open EJS Model" from the pop-up menu to examine the model equations of the motion. You must, of course, have EJS installed on your computer.
Describe the action of a split-ring commutator in a two-pole magnet setup, single-coil motor. Suggest the effect adding a soft-iron cylinder in the winding the coil.

Advanced Learner:

Please submit your remix model that model features that are not available in the existing virtual lab and share your model with the world through NTNUJAVA Virtual Physics Laboratory http://www.phy.ntnu.edu.tw/ntnujava/index.php?board=28.0. Impacting the world with your model today!

For Teachers

Direct Current Electrical Motor Model
Electric motors turn electricity into motion by exploiting electromagnetic induction. A current-carrying loop that is placed in a magnetic field experiences a turning effect.A simple direct current (DC) motor is illustrated here. ABCD is mounted on an axle PQ. The ends of the wire are connected to a split ring commutator at position X & Y. The commutator rotates with the loop. Two carbon brushes are made to press lightly against the commutators.
The motor features a external magnet (called the stator because it’s fixed in place) and an turning coil of wire called an armature ( rotor or coil, because it rotates). The armature, carrying current provided by the battery, is an electromagnet, because a current-carrying wire generates a magnetic field; invisible magnetic field lines are circulating all around the wire of the armature.
The key to producing motion is positioning the electromagnet within the magnetic field of the permanent magnet (its field runs from its north to south poles). The armature experiences a force described by the left hand rule. This interplay of magnetic fields and moving charged particles (the electrons in the current) results in the magnetic force (depicted by the green arrows) that makes the armature spin because of the torque. Use the slider current I to see what happens when the flow of current is reversed. The checkbox current flow & electron flow alows different visualization since I = d(Q)/dt and Q= number of charge*e. The Play & Pause button allows freezing the 3D view for visualizing these forces, for checking for consistency with the left hand rule .

Introduction

the following case describe a postive current i, postive B field, θ start = 90^o , split-ring commutator gap β₂= 80^o
The split-ring commutator allows electricity flows from the positive terminal of the battery through the circuit, passes through a copper brush [rectangle black boxes] to the commutator, then to the armature.
Postive current runs through ABCD as shown in the diagram (select the checkbox labels?), a +y direction force would act on AB. An -y direction force would act on CD. Taking moments about the axle conveniently, reveals a resultant torque T = Fmag*AD*cosθ acts on the coil loop. The coil loop rotates in an clockwise manner (view from battery side) starting 90^o until it reaches the θ = 170^o position (assuming that split ring angle are default at β₂ = 80^o). At this θ = 170+^o position, the current is cut off. However, the momentum of the loop carries it past the horizontal position until the coil loop reaches θ = 190o position. Contact between loop and split ring commutator is established again and the current in the coil loop is now reversed (note that current i is still positive). A -y direction force now acts on AB while a +y direction force acts on CD. The rotation motion is reinforced clockwise (view from battery side) as θ continues to rotate from 190^o to 350^o. At this θ = 350+^o position, the current is cut off. However, the momentum of the loop carries it past the verticall position until the coil loop reaches θ = 10^o position. Contact between loop and split ring commutator is established again and the current in the coil loop is now reversed back to same as at θ = 90^o. A a +y direction force would act on AB. An -y direction force would act on CD and the loop reaches θ = 90^o . The cycle repeats after θ = 90^o allowing the armature to experience torque in the reinforced direction at the right time to keep it spinning.
Function of split-ring commutator:
The purpose of the commutator is to reverses the direction of the current in the loop ABCD for every half a cycle.
A swing back and fro motion (maybe θ = 90^o increase to 270^o and decrease back to 90^o) is all you would get out of this motor if it weren't for the split-ring commutator — the circular metal device split into parts (shown here in teal with a gap of β₂) that connects the armature to the circuit.

Function of split-ring commutator:

The purpose of the commutator is to reverses the direction of the current in the loop ABCD for every half a cycle.
A swing back and fro motion (maybe θ = 90o increase to 270o and decrease back to 90o) is all you would get out of this motor if it weren't for the split-ring commutator — the circular metal device split into parts (shown here in teal with a gap of β2) that connects the armature to the circuit.

In other words

A electric motor is a device for transforming electrical energy into mechanical energy; an electric generator does the reverse, using mechanical energy to generate electricity. At the heart of both motors and generators is a wire coil in a magnetic field. In fact, the same device can be used as a motor or a generator.

When the device is used as a motor, a current is passed through the coil. The interaction of the magnetic field with the current causes the coil to spin. To use the device as a generator, the coil is spun, inducing a current in the coil.

Let's say we spin a coil of N turns and area A at a constant rate in a uniform magnetic field B. By Faraday's law, the induced emf is given by:

ε = -N d(BA cos(Φ))/dt

B and A are constants, and if the angular speed w of the loop is constant the angle is:
θ = wt

The induced emf is then:

ε = -NBA d(cos(wt))/dt = wNBA sin(wt) = εo sin(wt)

Spinning a loop in a magnetic field at a constant rate is an easy way to generate sinusoidally oscillating voltage...in other words, to generate AC electricity. The amplitude of the voltage is:
εo = wNBA

In North America, AC electricity from a wall socket has a frequency of 60 Hz. but in Singapore is 50 Hz The angular frequency of coils or magnets where the electricity is generated is therefore 60 Hz in USA or 50 Hz in Singapore.

To generate DC electricity, use the same kind of split-ring commutator used in a DC motor to ensure the polarity of the voltage is always the same. In a very simple DC generator with a single rotating loop, the voltage level would constantly fluctuate. The voltage from many loops (out of synch with each other) is usually added together to obtain a relatively steady voltage.

Rather than using a spinning coil in a constant magnetic field, another way to utilize electromagnetic induction is to keep the coil stationary and to spin permanent magnets (providing the magnetic field and flux) around the coil. A good example of this is the way power is generated, such as at a hydro-electric power plant. The energy of falling water is used to spin permanent magnets around a fixed loop, producing AC power.

Research

on an eariler Java version

ollection of photo taken by Kai Suah on a pilot lesson April 29th 2011 to test the worksheet and simulation, thanks bro!

Notes from Boon Chien

by using these 2 simulations separately, it is possible to achieve the look in the notes.

thus, i will not force the 2 simulations together as the handphone display cannot be optimised with 2 such layouts.

Use alternate Tab in your chrome browser, to play both both simulations!

Video

Electromagnetism (part 1): Force acting on a current-carrying conductor in a magnetic field by ETDtogo
Electromagnetism (part 2): Working Principles of a DC Motor by ETDtogo https://www.youtube.com/watch?v=e1Uz3Dcav-g
https://www.youtube.com/watch?v=w4tSAuhnw2E Electromagnetism (part 3): Function of a Split Ring by ETDtogo
http://youtu.be/t4qBcVSyVT0 Ejs Open Source Direct Current Electrical Motor Model
http://www.aps.org/programs/education/teachers/teachers-days/presentations/upload/090819-DC-motor-annotated-web.pdf Watch physicists Becky Thompson-Flagg and Ted Hodapp trade quips as they show how to take apart a small DC motor and find out how it works. They get the armature of the motor spinning with just a battery, a few wires, and a permanent magnet. The experiment in this video is the same one described in the DC Motor Annotated Activity Handout.

Other Resources

Credits

Fu-Kwun Hwang and Loo Kang Wee

FAQ: Understanding the DC Motor

How does a current-carrying coil in a magnetic field experience a turning effect?
When a current flows through a wire placed within a magnetic field, it experiences a magnetic force. This force is perpendicular to both the direction of the current and the magnetic field, as described by Fleming’s left-hand rule. In a coil, the different sides experience forces in different directions, resulting in a torque that causes the coil to rotate. The magnitude of this force is determined by the current, magnetic field strength, and length of the wire in the field.
What is a split-ring commutator and what is its role in a DC motor?
The split-ring commutator is a crucial component in a DC motor. It consists of a ring split into segments that connect to the ends of the coil and it rotates along with the coil. As the coil rotates, the split ring segments make contact with stationary brushes, which are connected to a power source. The commutator's function is to reverse the direction of current flow in the coil every half-rotation, ensuring that the torque on the coil is always in the same direction, allowing continuous rotation. Without it, the motor would simply swing back and forth instead of rotating continuously.
How can the turning effect of a DC motor be increased?
The turning effect or torque of the motor can be increased by:
Increasing the number of turns in the coil, which increases the overall force and thus the torque.
Increasing the current flowing through the coil, which results in a larger magnetic force.
Increasing the strength of the external magnetic field, which also leads to a larger magnetic force.
What is the function of a soft-iron cylinder in a DC motor?
Winding the coil around a soft-iron cylinder enhances the magnetic field. Soft iron is a ferromagnetic material, meaning that it easily becomes magnetized when placed in a magnetic field. This increases the magnetic flux that the coil experiences, resulting in a larger force and more effective turning of the coil.
What is the relationship between a DC motor and a generator?
A DC motor converts electrical energy into mechanical energy, using magnetic force to rotate a coil. A generator, on the other hand, converts mechanical energy into electrical energy. The basic principle of both is the interaction between a coil and a magnetic field. The same device can be used as either a motor or a generator. When used as a generator, a coil is spun within a magnetic field, inducing a current within it, a phenomenon described by Faraday's Law of Induction.
How is AC electricity generated?
AC electricity is typically generated by rotating a coil in a constant magnetic field, or by rotating a permanent magnet around a stationary coil, as used in power plants. The continuous rotation produces a sinusoidally oscillating voltage, resulting in AC electricity. The frequency of the voltage is determined by the rotation speed.
How can we generate DC electricity from the principles used to generate AC electricity?
To generate DC electricity, similar principles are used to AC, but a split-ring commutator is used, similar to that used in the DC motor. This ensures that the polarity of the generated voltage remains consistent. Multiple coils can also be used to smooth out the voltage fluctuations.
What is Fleming's Left-Hand Rule and how is it applied to the DC Motor?
Fleming's Left-Hand Rule is a mnemonic to determine the direction of the force on a current-carrying conductor in a magnetic field. In the rule, the thumb, index finger, and middle finger of the left hand are positioned perpendicular to each other. If the index finger points in the direction of the magnetic field, and the middle finger points in the direction of the current, the thumb points in the direction of the force. Applying this to a DC motor, it allows us to determine the direction of the magnetic force on each section of the coil in the magnetic field.

Breadcrumbs

⚙️Direct Current Motor or DC motor in 3D WebGL JavaScript HTML5 Applet Simulation Model with Boon Chien

Translations

Credits

Direct Current Motor Study Guide

Quiz

Quiz Answer Key

Essay Questions

Glossary of Key Terms

Apps

Sample Learning Goals

Exercises:

Advanced Learner:

For Teachers

Introduction

Function of split-ring commutator:

In other words

Notes from Boon Chien

Video

ICT Connection

Worksheets

Version:

Other Resources

Credits

FAQ: Understanding the DC Motor