# Physics 121.6 General Physics Applets

Here you will find some applets and other content from the web that will help you learn some of the most important concepts. Many of them involve simulations you can run on your computer. For many of these you will need to be using a browser that has "Java" enabled. For some you will need the "Shockwave" plugin.

In exercises involving applets, click on the "Run Applet..." link to run the applet. Note: Many applets take some time to load; up to a minute or so, depending on your connection speed and network traffic. (They will in general be loading from somewhere outside Saskatchewan.) So be patient, you may be facing a blank box on your screen until the applet loads and starts running. After playing with the Applet, click your browser's "back" button to return to the Physics 121.6 Applet page.

 Name and Link Applets 1 - Graphs of Position and velocity Applets 2 - Vector Addition Applets 3 - Projectile Motion Applets 4 - Circular Motion Applets 5 - Relative Motion Applets 6 - Forces and Newtons Laws Applets 7 - Newton's Mountain Cannon Applets 8 - Force and Work Applets 9 - Integration and area under a curve. Applets 10 - Conservation of Energy for a Pendulum Applets 11 - Collisions Applets 12 - Motion of the Centre of Mass Applets 13 - Rolling Motion Applets 14 - Vector or Cross Product Applets 15 - Motion under different kinds of Force Applets 16 - Kepler's Laws Applets 17 - The Buoyant Force Applets 18 - SHM and Circular Motion Applets 19 - Simple Pendulum Applets 20 - Damped Oscillations Applets 21 - Forced Oscillations Applets 22 - Transverse and Lontitudinal Waves Applets 23 - The Reflection and Transmission of Waves Applets 24 - The Doppler Effect Applets 25 - The Superposition of Waves Applets 26 - Standing Waves Applets 27 - Resonance Applets 28 - Beats Applets 29 - The Sound of Complex Waveforms Applets 30 - Electromagnetic Wave Applets 31 - Reflection and Refraction Applets 32 - Mirror and Lenses Applets 33 - Thin Lens Combinations Applets 34 - Accomodation Applets 35 - Young's Double Slit Interference Applets 36 - Single Slit Diffraction Applets 37 - Thin Film Interference and Diffraction Patterns Applets 38 - Electric Field Lines and Equipotential Surfaces Applets 39 - Electric Circuits Applets 40 - Magnetic Fields Applets 41 - The Lorentz force Applets 42 - Motors and Generators

The following is a list of applet collections that you may find useful. In the table above however I have links to a few of the many applets available on the web that I think are most useful in illustrating the concepts of this course.

### Applets 1 - Graphs of Position and Velocity

This Applet shows a cow on roller skates! You can give the cow an initial position, an initial velocity and an initial acceleration and then you can see what happened when you click on "RUN". The applet then draws a position verses time graph and a velocity verses time graph of the motion. Note: position is labeled P in the applet rather than x as we use. Also the applet will not allow you to give a negative initial velocity.

Note the shape of the position vs. time graph and the velocity verses time graph for each of the following cases. Also note the green velocity vector that is drawn as the applet runs.

• Try different non-zero initial velocities with zero acceleration.
• Try zero initial velocity and non-zero positive acceleration.
• Try a positive initial velocity and negative acceleration.
• Play around with other combinations.

This second applet displays much the same thing. But as you move the mouse around you can see how the slope of the position verses time graph is the velocity and how the slope of the velocity verses time graph is the acceleration. You can also change the acceleration through the motion. Try it and see what results...

### Applets 2 - Vector Addition

This Shockwave applet shows the addition of two vectors (Red vector + Green vector = Blue vector). You can move the Red and Green vectors around and change their direction and size and see the resultant Blue vector.
• Notice the components of the vectors are displayed at the top of the display; labeled "Rectangular coordinates". (The first number is the x-component and the second number is the y-component.) Check that the components of the Blue vector components are equal to the sum of the Red and Green vector components.
• The magnitude and direction of each vector is also given; labeled "Polar coordinates".  (The first number is the magnitude and the second number is the angle counterclockwise from the +x axis direction.) Check that the magnitude and direction given are correct given the components.

Another applet which shows much the same thing in a slightly different way....

### Applets 3 - Projectile Motion

This Applet shows the path of a cannonball fired into the air over a horizontal ground. You can change the initial speed of the cannonball, the angle at which the cannonball is fired, and the mass of the cannonball. Suggested exercises using the Applet appear with the applet itself.

Here is another applet showing projectile motion with no air resistance. In this one you can also change the height of the launch position.

### Applets 4 - Circular Motion

This applet shows the development of the idea that the centripetal acceleration points toward the centre of the circle. The position vector of an object moving in a circle at a constant speed at time intervals. You can successively show the position vector r, the displacement dr, the instantaneous velocity v, the change in velocity vector dr, and the acceleration a. You will see that a points in the opposite direction to r.

### Applets 5 - Relative Motion

This applet demonstrates relative motion. You can dynamically change the speed of the boat and the direction of the boat (as well as the speed of the river. See how the velocity of the boat relative to the bank changes as you change these parameters.

This applet also demonstrates relative motion. It can show the motion of a boat in a flowing river, and a man who walks along the bank or swims through the water. By moving the mouse you can see the motions relative to difference frames of reference. Read the instructions to see how to change the velocities of the boat, water or man. Note that velocities can only be changed when the motion is suspended by clicking the right mouse button.

The applet shows what motion would look like from a rotating frame of reference (a non-inertial frame). From the point of view of the rotating frame of reference it appears that there are fictitious force at play, the Centrifugal force and the Coriolis Force.

### Applets 6 - Forces and Newtons Laws

This applet show a box on an inclined plane. You can change the mass of the box and the angle of the plane (labeled phi in "Grad" but it is actually degrees). You can also change the coefficients of friction between the box and the plane (labeled "Reib" in the applet). Start with no friction - i.e. make the coefficients zero. Calculate the acceleration you expect and see that the applet give the expected result. Now add friction. Under what condition will the box not accelerate?

This next applets also has a box on an inclined plane but now attached to another hanging mass via a sting and a pulley. The sting and pulley are assumed to be massless and frictionless. Once again start with zero friction and play with the masses and angle of the plane to see that the masses can be made to accelerate in either direction. Calculate the acceleration you expect and see that the applet predicts the same result. Then add some friction.

This last Applet shows another example where friction forces are present.
Mass m3 = 10 kg hangs by a massless string which goes over a massless and frictionless pulley and is attached to a mass m2 = 10 kg upon which another mass m1 = 10 kg sits. You can set the coefficient of friction, which is the same between the mass m2 and the surface and between the two masses. In this simulation the coefficient of static friction is equal to the coefficient of kinetic friction. Then run the simulation and see what happens. (Note: When setting the coefficient of friction, be sure to hit "enter" after entering the number to make the new value take effect.)

Do the following:

• Set the coefficient of friction to 0.2. See that the two masses remain together. Calculate the acceleration of the two masses for this case. [ Answer: 1.96 m/s2]
• Set the coefficient of friction to 0.1. See what happens to the two masses now. Calculate the acceleration of the mass  m2 while the mass m3 is still on top of it. [Answer: 3.43 m/s2] Then calculate the acceleration of the mass  m2 after the mass m3 has fallen off it. [Answer: 4.41 m/s2]
• Note the vector diagram at the left of the simulation. It shows the vector sum of all the forces on the mass m2.
[Hint: When doing the calculations, note that the three masses are the same (call it m). You don't even need to know that m = 10 kg.]

### Applets 7 - Newton's Mountain Cannon

This Applet shows the path of a cannonball fired from the top of a tall mountain. Instructions for using the Applet appear with the applet itself.

### Applets 8 - Force and Work

This applet shows you the total work that you do on a box as you move it around. You can move it sideways and vertically. When you slide it on the surface you can choose whether there is friction present or not.

This applet show the scaler product or dot product. Drag the head of the vector arrow the change its magnitude and direction. Drag the line part of the vectors to change only its angle and keep the magnitude constant. The magnitude of the resulting dot product is displayed by the bar at the right.

### Applets 9 - Integration and the area under a curve.

This applet shows the area under a curve. As you drag the red dot on the left graph to the right you will see the area under the curve plotted on the right graph. That graph represent the integral under the curve shown on the left graph. Once you have done that you can see that the slope of the curve on the right is given by the curve on the left. Thus you can see that integration is the inverse operation to differentiation.

### Applets 10 - Conservation of Energy for a Pendulum

This Applet shows a pendulum swinging back and forth. Under the pendulum is shown a continuous plot of the Kinetic Energy (labeled K and shown in red) of the pendulum bob and the Gravitational Potential Energy (labeled U and shown in blue) of the bob. The simulation assumes no energy is lost to friction as the bob swings back and forth. If you click on the gray area you can change the initial position of the bob. By clicking near the red dot you can change the length of the pendulum.

Things to note:

• The total mechanical energy is at all times constant. Why?
• What force other than gravity acts on the bob as it swings? Why doesn't this force matter when considering conservation of energy?
• Note that the red vector shows the instantaneous velocity of the bob at all times. If you click on the "show" check box you will see a blue vector which is the force of gravity vector. the green vectors are the components of the force of gravity along the line of the string and perpendicular to the string.

### Applets 11 - Collisions

This first Applet show the collision between two bodies in 1-dimension. This is similar to the simulation of the collision between two cars we showed in class. You can change:
• The velocities of each body.
• The mass of each body.
• The elasticity of the collision - 100% elastic means an elastic collision. 0% elastic means the two bodies stick together after the collision, which is a perfectly inelastic collision.
Try changing all the parameters and observe how the collision looks different in each case. Notice how momentum is always conserved, but the total kinetic energy is only conserved when there is an elastic collision.

This second Applet shows the elastic collision between two balls and illustrates the Conservation of Momentum and Conservation of Kinetic Energy. Suggestions for using the Applet appear with the applet itself.

### Applets 12 - Motion of the Centre of Mass

This applet show the motion of the centre of mass of a complicated object that is rotating. Click "start" to start the applet. You can then run it with different initial velocity, angular speed and mass ratio that make up the object. Note that the centre of mass follows the same parabolic path in each case (air resistance is ignored).

### Applets 13 - Rolling motion

This Applet shows a wheel rolling without slipping. There are many things displayed in this applet and it can be confusing so we will concentrate on only one thing at a time.
• First, look at the rolling wheel at the bottom of the screen. The white vector represents the velocity of the centre of the wheel. The red vector is the velocity of a point on the rim of the wheel relative to the centre of the wheel. Notice that it is always at a tangent to the rim of the wheel and at right angles to the radius, denoted by the yellow arrow. The gray vector is the sum of the red vector and the white vector and is the total velocity of a point on the rim of the wheel relative to the ground. Notice that this velocity (the gray vector) is not constant, it is constantly changing. Note that at the top of the wheel this velocity has greatest magnitude, equal to twice the velocity of the wheel. At the bottom of the wheel this total velocity is instantaneously zero. At other points on the wheel it has a different velocity. The green line at the bottom show the complicated motion of a point on the rim of a rolling wheel.
• The three circles at the top are representations of simple circular motion at a constant speed. The left hand one shows the actual circular motion. The yellow line is the radius and the red vector is the velocity a point going in a circle at a constant speed. The green line shows the path of the point. The centre circle shows what the velocity vector is doing as time goes on. If we imaging the tail of the velocity vector fixed at one point we see that the velocity vector is also going around in a circle. Notice that it is always pointing in the same direction at the velocity vector in the left circle. The blue vector acceleration of the point. The change in velocity in a small time interval is always perpendicular to the velocity vector. So if we show the acceleration vector on the point going in a circle, as is done in the right hand circle, we see that it always points toward the centre of the circle. This is the centripetal acceleration.

This simpler applet than the one above shows some of the same things in a slightly easier to view manner.

### Applets 14 - The Vector or Cross Product

This applet give a three dimensional representation of the Cross Product of two vectors A and B. You can change the components of either vector and see the resulting Cross product. You will need to adjust one of the sliders to initially bring the applet to life.

### Applets 15 - Motion under different kinds of force

This applet show the motion of a particle under many different types of forces. E.g. a constant force (as in projectile motion) and a force always perpendicular to velocity (circular motion). But I introduce it here specifically to show the motion under a central force that is proportional to 1/r2, which is the type of motion seen under gravity.
The instructions on how to set up the applet and get it started are under the applet itself. Play around with the different types of forces. Note particularly that the 1/r2 central force gives a closed orbit that is an ellipse.

### Applets 16 - Kepler's Laws

Kepler's First Law - Planets move in ellipses

Kepler's Second Law - Planets sweep out equal areas in equal times.

### Applet 17 - The buoyant force

This applet show the change in apparent weight of an object, as measured by a spring gauge, as it is immersed in a fluid.

### Applet 18 - SHM and Circular Motion

This Applet shows the relationship between uniform circular motion and Simple Harmonic Motion (SHM). The masses on the springs at the bottom and the side oscillate in SHM. The thumbtack on the table rotates with the same period. You can see the relationship between the projection of the circular motion and the oscillating masses. The red vector on the blue mass indicates its velocity. Notice that it is always the same as the blue vector on the rotating thumbtack, which is the projection on the y-axis of the red vector on the thumbtack which is the velocity of the thumbtack. i.e. the y-component of the velocity. You can pause the motion at any time by clicking and holding down the left mouse button in any part of the gray box. Notice also that the graph of the position of the blue mass, and the y position of the thumbtack, as a function of time looks like a sine function, a signature of SHM.

This second applet shows much the same thing.

### Applet 19 - Simple Pendulum

Look again at the applet for the simple pendulum. You can change the length of the pendulum, its mass and the acceleration due to gravity. The resulting period of the pendulum is shown in the upper left hand corner. Notice how it varies as you change the above quantities. Notice too what happens to the period when you make the amplitude of the pendulum's swing very large. The approximation of small angle swings is not valid then.

### Applet 20 - Damped Oscillations

This applet shows simple harmonic oscillations with a damping factor for the case where the damping force is proportional to the speed. Initially the damping factor, b, is zero. Slowly increase b to find the point where oscillations cease.

### Applet 21 - Forced Oscillations

Initially the end of the spring is wiggled at a frequency that is not equal to the natural frequency of the mass and spring system. notice that the amplitude of the resulting oscillations are not very large. Increase the driving frequency (the exciter angular frequency in the applet) and note what happens. When the driving frequency is close to the natural frequency of the system the amplitude of the vibrations can rapidly become large.

A dramatic example of forced oscillations - The Tacoma Narrows Bridge - collapsed 1940. (avi movie).

### Applets 22 - Transverse and Longitudinal Waves

A graphic illustration of the two basic types of waves - Transverse and Longitudinal. You can change the wavelength of the waves by changing the wave number k (the wavelength is proportional to 1/k so a larger k gives a shorter wavelength) and you can also change the frequency of the waves. The "mixture" picture shows what a combination Transverse and Longitudinal wave would look like. Water waves on the ocean are actually waves of this type.

Here are two more applets that demonstrate Transverse waves (Run Applet...) and Longitudinal waves (Run Applet...)

And two more demonstrating Transverse waves (Run Applet...) and Longitudinal waves (Run Applet...)

### Applets 23 - The Reflection and Transmission of Waves

This applet show the reflection of a wave pulse from a fixed end and from a free end. It can also show what happens when a wave pulse is incident on a join in two ropes that have different thicknesses, and therefore different speeds of propagation.

This applet shows the reflection of a wave pulse or a periodic wave from either a fixed end or a free end.

### Applets 24 - The Doppler Effect

This applet show a moving source of sound (the red dot). It also shows the wave fronts moving out from the place where they were emitted. You can change the speed of sound and the speed of the source (in relative units).
• Make the speed of the source less that the speed of sound and note the bunching up of the wave front in front of the source, and the spreading out of the wave fronts behind the source. Play with different values. you can also change the period of sound souse (1/frequency).
• When the speed of the sound source is greater than the speed of sound you are "breaking the sound barrier". Notice the shock wave fronts heading out from the source in a V formation. This is what happens when a plane travels faster than the speed of sound. The shock wave is the "sonic boom".

Another Doppler Effect applet:

Sound files:

### Applets 25 - The Superposition of Waves

The first applet show the superposition of two wave pulses. One from the left and one from the right. Notice what happens when they overlap each other. You can flip a pulse upside down by clicking under it. Click and hold the right mouse button to pause the simulation.

Another applet showing the superposition of two wave pulses. You can step through the animation frame by frame. Choose Phase: Out to see the animation with one pulse upside down.

This applet shows the same thing as the above applet, except with longitudinal waves.

This applet show the two dimensional interference of water waves from two coherent sources. This is rather like the interference of sound waves from two speakers that are in phase. You can see how the different path difference results in constructive or destructive interference at different points.

### Applets 26 - Standing waves

This applet can show the standing wave pattern such as will exist in guitar string (both ends fixed). It can also shows the pattern of a sound wave in an organ pipe (one end free or both ends free). Do the following:

With both ends fixed (it is probably easiest to see if you don't check "components" and "particles".)

• Observe the pattern for each component separately each set to 100% and the other 3 set to 0%.
• Put in extra components with the fundamental and see how complicated the pattern can become. This is what would occur in a real guitar string. You can use the applet in Applets 28 to hear what a complex pattern like this would sound like. Check "components" to see the individual overtones that add to give the observed pattern.
• Note: In this case:
• first overtone = 2nd harmonic
• second overtone = 3rd harmonic
• third overtone = 4th harmonic
With one end fixed.
• Repeat the exercises you did for both ends fixed.
• Note: In this case:
• first overtone = 3rd harmonic
• second overtone = 5rd harmonic
• third overtone = 7th harmonic
With both ends free.
• This simulation does not show the correct thing in this case. It just shows a traveling wave, not a standing wave.

### Applets 27 - Resonance

This applet show what happens to a string, which is fixed at both ends, when it is wiggled at a given frequency. Change the frequency and you will find those frequencies that give large amplitude standing waves. These are the resonance frequencies which are equal to the harmonic frequencies of the string fixed at both end.

### Applets 28 - Beats

This applet shows the phenomenon of Beats. Change the frequencies of the two waves and see how the sum changes. Read the notes below the applet for more information.

This Applet shows the result as a function of time at a fixed point in space.

• W1 and W1 are the angular frequencies of the two waves.
• A0_1 and A0_2 are the amplitudes of the two waves.
• Phi_1 and Phi_2 are the phases of the two waves (in radians). Don't worry too much about these, we don't discuss phases much in this course. You can make the waves 180 degrees out of phase by putting Phi_1 = 0 and Phi_2 = 3.14 (pi). Try it when W1 = W1 and A0_1 = A0_2.
• Try making W1 = W2 = 0.20, with A0_1 = A0_2 = 30 and Phi_1 = Phi_2 = 0. Observe the pattern then change W2 = 0.22 and see the change. This is the Beats phenomenon.

### Applets 29 - The Sound of Complex Waveforms

This applet will allow you to see and hear a complex waveform. You can change the amounts of each harmonic and see the shape of the waveform as a function of time. By pressing the "play" button you can also hear the resulting sound. Checking the box in the top right-hand corner also show the intensity of the wave (the square of the wave amplitude) in yellow. The green sliders (labeled "cos") add waves that are 90°  out of phase with the blue slider waves (labeled "sin").

(It is probably a good idea to click "stop" before leaving the page - I have found that my computer's sound card sometimes gets "stuck" on otherwise.)

Different musical instruments have different sounds because they have different amounts of the various harmonics even though they may be playing the same fundamental frequency.

### Applets 30 - Electromagnetic Wave

This Java applet simply shows you what an electromagnetic wave might look like from an antenna. You can see how the electric and magnetic field vectors oscillate.

### Applets 31 - Reflection and Refraction

This Java applet shows you rays and waves reflecting and refracting off an interface between two materials. You can change which materials are displayed from a drop down list or you can put in your own ratio of the refractive indexes. You can also change the angle of incidence by dragging the black dot at the top.
Things to note:
• See how the angle of reflection and refraction are form by the waves radiating out from the interface.
• Note the different speeds of the waves in the different materials.
• See that total internal reflection occurs when the conditions are right. What conditions are these?
The simulation will also show sound waves as well as light.

This applet shows how rays of light are reflected and refracted by a water droplet forming the dispersion that results in a rainbow.

### Applets 32 - Mirrors and Lenses

This Java applet allows you to play with Mirrors and Lenses, both  concave and convex mirror and converging and diverging lenses. You can move the mirror or lens around (by dragging it) and you can move the object and change its size (by dragging the object arrow head). The object distance is labeled p and the image distance is labeled q in this simulation. Clicking on the + or - box you can change the mirror from concave to convex or change the lens from being converging to diverging. You can also change the focal length f.
• The main thing is to play with all the combinations. Note where the image is relative to the focal points of the lens. The distance of 2f is also shown.
• Note in each situation whether the image is real or virtual, upright or inverted, reduced or enlarged. The calculated magnification m is also displayed.
• The principal rays are also drawn. Note how to find the image yourself using the principal rays. (You won't have this applet in an exam!)
• The default is to show paraxial rays. By unchecking this box you can see the spherical abberation effects.

Also check out this applet which shows rays of light passing through a thick lens. You can change the thickness of the the lens and see how rays of light parallel to the principal axis are affected. Notice that if you change the distance of the light rays from the principal axis the focal point changes (this is spherical abberation), but if the rays of light are restricted to being close to the principal axis the focal point is approximately at the same position.

### Applets 33 - Thin Lens Combinations

This Java applet allows you to see a wider range of effects than you can with the previous applet. You can see the effect of a two-dimensional object rather than a one dimensional one. Also you can see the effect of having two lenses instead of one.

The object is a box with four coloured dots at the corners and white lines.

• Clicking on the green dot will change which corner's rays are displayed.
• Dragging the red dot will move the box around.
• Dragging the blue dot will change the size and shape of the box.
• Dragging anywhere in the lens will move the lens.
• Dragging the hollow gray circle will change the focal length of the lens.
• The object distance for the displayed coloured corner is labeled p and the image distance is labeled q.
• Clicking with the right mouse button will introduce a second lens (clicking again will remove it).
• The second lens's position and focal length can be changed in the same manner as the first lens.
• The intermediate image (through the first lens, ignoring the second lens) is shown with hollow coloured circles at the corners and gray lines.

### Applets 34 - Accommodation

This simple Shockwave Applet show the accommodation effect of the eye. As the distance of the object changes the focal length of the eye must change since the image distance is fixed.

### Applets 35 - Young's Double Slit Interference

This applet show the interference of light (Young's double slit experiment) for various wavelengths, slit separations and distances to a screen.

The following applet show what happens as you add extra slits (or sources) to the two slits. Many slits becomes a Diffraction grating.

Finally a look at one of the weird quantum effects associated with the double slit experiment. It works, not only with light (which is actually quantized particles known as photons, as well as behaving like a wave), but also with real particles such as electrons. It is a video clip from the movie "What the Bleep do We Know?"

Play Movie...

### Applets 36 - Single Slit Diffraction

This applet show the diffraction patter obtained from a single slit on a screen. When the applet start you see the experiment. Adjust the slit-to-screen distance, the slit width, and the wavelength of the light to see the effect on the diffraction pattern.
Then choose results from the menu to see a plot of the intensity distribution you see on the screen. If you move you mouse up into the graph part of the screen, and move it from side to side, you will see how the phaser addition of several dozen phasors from different part of the slit add to give the final amplitude of the wave at each place on the screen.

### Applets 37 - Thin-film Interference and Diffraction Patterns

This applet shows the thin-film interference effect as applied to the lens coating situation.

This applet allows you to create you own hole pattern in a slide, and then see the diffraction pattern you would get. Read the instructions with the applet to see how to use it.

### Applets 38 - Electric Field Lines and Equipotential Surfaces

This applet shows the electric field lines around one or two charges. You can change the sign of the charges. With two charges you can change the sign and magnitude of one of the charges. You can also choose to display the equipotential surfaces.
Note:
• When the charge is larger you have larger electric fields.
• When the electric field lines are closer together the magnitude of the field is largest.
• When you have two opposite charges you have a dipole.
• The equipotential surfaces are always perpendicular to the electric field lines.

Another applet that shows in more detail all manner of electrostatic quantities. Select "Setup: single charge" or "Setup: Dipole Charge" or "Setup: Double Charge" to show the same things as the previous applet. Select "Show E lines". You can select many other charge distributions as well.

This next applet is part of the Physics 2000 website. Scroll down to find the applet which is a rectangle with a positive and negative charge in it. Click anywhere in the rectangle to see the force on a test positive charge if it is placed at that point (Note: the text near the applets says you are placing electrons. This is not correct The force on an electron would be toward the positive charge not away from it). Place several and see that the force is strongest nearest to the charges. Note the direction of the forces. Place many test charges and see the pattern created. Press 'R' to place many at one time. You will build up a picture of the electric field lines. Press 'L' and you will see the electric field lines.

### Applets 39 - Electric Circuits

This Shockwave applet allows you to make up your own electric circuits and see current flow and measure the voltage and current in different parts of the circuit. Follow the instructions with the applet.
Note:
• The wires do have a finite but small resistance.
• Use Control-left click to switch a switch.

### Applets 40 - Magnetic Fields

This applet shows the magnetic field around a bar magnet. Move the compass needle around to find the magnetic field at each place.

This applet shows the magnetic field around a current carrying wire. Again move the compass needle around.

### Applets 41 - Lorentz Force

This applet shows the path of a charged particle in a magnetic field. You can change the charge and velocity of the particle and the magnetic field.

Another applet showing the force on a charged particle moving in a magnetic field.

This applet shows the Lorentz (or Magnetic) Force on a current carrying wire.

### Applets 42 - Motors and Generators

This applet illustrates the principle of a simple direct current electric motor.

This applet illustrates the principle of an electric generator. You can change it from an AC generator to a DC generator.