Lab Report Day 23 - Ampere, Lenzs, Faraday, Galvanometer

Direction of Force On Wires

In this lab, we connect two wires to a power supply. The force due to the magnetic field from wire 1 on wire 2 and from wire 2 on wire 1 can be found by the definition of magnetic force and magnetic field.

We make few predictions whether the two wires will repel or attract to each other when they have same direction current or opposite direction. When the current in the wires has the same direction, we predict that the wires will attract each other by the right hand rule.

Our prediction is correct. We observe that the wires move towards each other. On a charged line, the magnetic field are created to be counterclockwise. On its left, the magnetic field is pointing out. On its right, the magnetic is pointing inward. Using the right hand rule, we can see that the forces are acting toward each other. 

When the current in the wires has the opposite direction, we predict that the wires will repel each other by the right hand rule.

Again, our prediction is correct.

Magnetic Field Sensor (Solenoid)

In this lab, we use wires to bend into loops on the test tubes to form a coil. When we connect it to a power supply, it acts as an electromagnet, and it will generate a magnetic field. With LoggerPro, we can see that the magnetic field in a loop is proportional to the number of loops and the current running through the loops.

Set Up for the lab

In this lab, we use a magnetic field sensor to measure the strength of the magnetic field. We can get a max magnetic field in the end of the solenoid. 

As seen in the picture above, the more loops we have, the higher the magnetic field is.

From this we get the formula for a magnetic field in a solenoid to be

Galvanometer

A galvanometer is used for detecting electric current. It can measure the inducted current.

This is what a galvanometer looks like.

We list the factors that can change the current induced in a coil.

After playing around with the coil, a magnet and the galvanometer, we can see that what effect current are: velocity of pulling out/pushing in, number of turns of the coil, magnetic field, and the area between the magnet and coil.  

Lenzs’ Law: Aluminum and Plastic Tubes 

For this lab, we put them through two tubes at the same time; one is made of aluminum and one is made of plastic. We predicted that when the magnetic object is dropped in the aluminum tube it would fall slower since it will product a force reject it to leave.

When we do the experiment, we find our prediction to be right, the magnetic object fall faster in the plastic tube and significantly slower in the aluminum tube. Lenzs’ law states that a magnetic field always opposes an induced magnetic field. The magnet induces a current when it moves through a coil (aluminum tube) and as a result, it will produce an upward force. When the magnetic object is placed in the plastic tube, both objects drop at the same time since it does not induce current.  

Faraday: Ring

For this lab, we have an aluminum ring. When we increase the current flowing into it, the ring flies. This is a force acting on it. The current running through the coil creates a magnetic field in that ring, going up, and that magnetic field induces a current which creates another magnetic field going the opposite direction, down. The two magnetic fields are repelling each other which makes it fly. Also, it is warm because the current is running through it. Then, we place the ring with another ring with slit on it.

When it is connect to the power supply, nothing happens. Then, we put a coil with a light bulb to it. When we connect the larger coil with power supply, it will induce a current and lights up the light bulb.

Magnet and Rod:

In this lab, we will see how the current is affected with the area changing. Current is applied to the two rails. A large magnet is placed in between the two rails. We place an aluminum rod  on the two rails. 

When a current goes through the rod, there is a magnetic field in a circle around that rod. When there is a current, the rod moves since it has a force acting on it by the right hand rule.  The area of the magnetic field will change. When the area gets larger and larger, we can get an induced current. 

Measuring earth magnetic pole:

In today's lab, we use LoggerPro and the magnetic sensor to measure the earth magnetic pole. We connect logger pro to magnetic sensor and graph the picture as we moved around the classroom.

As the data shown in the following picture, we find the north side of the classroom which the sensor has the highest measurement. Therefore, we can conclude that the north of earth has the strongest magnetic field. 

Summary:

In today's lab, we learn how to measure the magnetic field strength. We learn how induction and Lenzs' Law works. We practice to use right hand rule more. 

Lab Report Day 22 - Magnetism, Motor, Forces on a Line of Charge, Compass and Magnetic Demo

2 ways to destroy a Magnet

We talk about how to destroy magnetic. We just need to make the electrons not in order. 

Magnetism

In this demo, Professor Mason has two coils of wire that can become magnetic when connect to a power supply.  A switch is attached to the two coils to change the direction of magnet. When the switch is on or off, it oscillates and stop. In order to keep the magnet spinning, we need to keep switching it to on and off. This is how a motor works.

In a two pole motor like the one above, we have to turn on and off ourselves. However, in a 3 pole motor, there is always some torque and it will keep working forever as long as there is power supply connect to it. This is how a motor work. 

Motor

Next, we are given a motor that is powered by electric current and magnetic field. Two magnets are places with opposite poles in order to power the motor. A commutator stops the current from going through as it spins. Without a commutator, it will just wiggle back and forth. The commutator makes it spin around by reversing the magnetic field for a split second allowing it to turn. 

When power supply is applied, the motor turns one way. When the power supply is reversed, the motor turns another way. 

From this model, we can see that direction of current flow dictates the direction of the motor.

Next, we were only given a magnet, two paper clips, a cup and a power source. We will make our own commutator by sanding down 360 degrees around the wire on one side while only sanding down half of the other side. This allows the current to stop every half turn. We have get a chance to make it work well. 

 Magnetic Field 

We place compasses around a metal rod when there is current going through it. The picture below shows that when the current is coming out of the page, the magnetic field is counter-clockwise around the current. When the current is going into the page, the magnetic field goes around the current is clockwise . Using this, we can construct a right hand rule where your thumb points where the current is going and the way that your fingers curl show where the magnetic field is. 


When there is only one wire, the magnet points toward the wire. Within the wires the magnetic fields cancel each other.  And when the wires are in in parallel, the magnetic field will be doubled. 
Based on observation, we can conclude that a line of current produce a circle of magnetic field, and a circle of current produce a line of magnetic field. 

Summary:

We learn the how current can affect magnetic field. We learn how motors work and we are able to build our own motor. We can apply right hand rule in more situations. 

Lab Report Day 21 - No Class

Professor Mason is not here today. No lab today.

Lab Report Day 20 - Magnetic Field, Lorentz Force

Magnetic Field Lines Around a Magnet


Using a compass, we can draw the direction of a bar magnet as we rotated the compass around the magnet. North is attracted to South, and South is attracted to North. We can also draw the magnetic field line by putting a compass around it. 
Gauss's  Law in Magnet is defined as ∫B∙dA. ∫B∙dA=0 because there is no monopole, in every single magnet, there will always be south pole and north pole. Thus, the net flux is always zero. 



Afterwards, we spray some Fe power near a magnet to see the magnetic field. 
Magnetic fields go from positive to negative. 


Electric Field Lines


Lorentz Force

Using a magnet, professor Mason use a magnet to approach the green spot of electrons on the oscilloscope from two different directions. When it's from the sides, we can see that the electrons would move perpendicular to the magnet.When the magnet is directly towards it,  the spot does not move. This shows that  the velocity and the magnetic field needs to be perpendicular, giving us the equation F=qVxB or F=qvBsinθ. The right hand rule can also be used in order to help determine the direction of the force.

Lorentz Force Large Magnet Demo

For this lab, Professor Mason brought out a large magnet and set up a copper wire across and in between the magnet.

A large current goes across the wire and we see that the wire moves. It seemed to jump up.

Then we reverse the direction of current. We can see that the wire jumps down.
The velocity of the electrons is going through the wire, the direction of the magnetic field is going across the poles of the magnet, and the force is perpendicular to the velocity and magnetic field (Lorentz Force= F=qVxB or F=qvBsinθ). This copper wire is a current carrying wire, which is a line of electrons moving with some velocity.

 Finding Net Force

For this lab, we find the total force on a wire by using a spreadsheet. A semicircular wire is cut into 15 segments. θ, sinθ , and F are found for each segment and add them up. (F= IL x B) It can be observed that there is a maximum first at 90 degrees and a minimum on the sides. 

Summary:
In today's class,we learn how to find a force caused by Magnetic Field. We learn how to use the right hand rule to determine the direction of L, B or F. We learn how to solve problems.

Lab Report Day 19 - Analog and Digital Electronics,LED Circuit, Low Pass Filter, Amplifier

Analog and Digital Electronics

For this lab, a oscilloscope is hooked up to a audio input wire connected to a phone and a speaker. We download a sound generator app, and it generates various frequencies.We observe the wave on a oscilloscope.

The set up of our experiment. 

The wave the phone generates. 

The wave the phone generates. 

 The max voltage that the phone will put out through the audio jack is found to be 0.04V.

Wave when we play music.

LED Circuit

We build a circuit on the board in order to light a LED. We first connect a resistor and LED to the circuit board and then connect to a power supply. When the power is on, the bulb lights. When we increase the voltage from 3V to 4.5V, we can see that the bulb gets brighter since it has higher current.

The set up of this experiment. 

From this, we can see that a LED is a diode. When the power reverse the power supply, the bulb does not light because the depletion region is getting larder. 

We then add a switch to it. When we do not push on the switch, it is not on. 

When we push the switch, it lights up.

Low Pass Filter

For the low pass filter lab, a circuit was set up using a 0.1 uF capacitor and a 22K resistor. The circuit is connected to the oscilloscope and the phone with a tone generator app. It can be seen that resistors are not frequency dependent and capacitors are.

Graph of Voltage vs. Frequency

Amplifier to Boost Current from an Audio Player

The set up of building an amplifier

We are asked to build an amplifier on the circuit board in order to take the lower power signal from the phone and produce a wave with greater power.
We use  two 0.1 uF capacitors, one 3K resistor, one 2.2 Meg resistor, 500 pF capacitor and a 0.22 uF transistor on a circuit board. When we connect to the speaker,we do not hear the sound . We use an oscilloscope in order to find the error in the circuit. It can be the quality of the speaker is not good. 

Summary: 

In today's class, we learn more about the oscilloscope. We know how to build a circuit on a circuit board. We know how a low pass filter works, and we learn how to build an amplifier.

5% Extra Credit on Midterm 2

Help with the Kitchen stuff