Lenz's Law and Faraday's law (0514)

Lenz's Law and Faraday's Law

After we had the direction of the magnetic field, we could use the regular right hand rule ( of three vectors) to find the direction of the force. Interestingly, the magnetic forces will pull the wires together ( for DC source).

Then the professor shows us the experiment. When closing the switch, and the two lines were charged, they get closer thant no charged.

Then we make a prediction, we think that because there are forces that makes them closer, but actually, because of the power is alternating current, so there is no force.

Then in these two photos, the professor use logger pro to make a graph of the change of magnetic field as time changes. and we draw the north and south poles in the graph.Professor then performed the experiment by switching on the power supply causing an alternating current in the two parallel lines. There are in fact no net forces acting as there due to the alternating current. Then he uses logger pro to show magnetic field in respect to time.  Two cycles here are observed in which we can interpret the magnetic field oscillations caused by the north and south poles by applying Faraday's law

We use logger pro to collect data and make a graph in this photo,

in this photo, we calculate the flux of magnet. the first one, because the B and A are parallel, so the flux is 0, and the second one, because they are perpendicular so the flux=B*a*b

The professor use a magnet to cross the loops and when it enter or leave the loops, the dash board will change. Professor uses a bar magnet and galvanometer and allowed the magnet to go back and forth causing movement (changing magnetic fields) which stimulates a current seen in the movement of the meter through induction. As he stops in the center of the coil there is no change in the meter when it stay in the loops, it doesn't change 

We list 4 reasons that can influence the dash board.If we want to maximize the current on an induced EMF we can add more loops on the coil, have a bigger loop by increasing the area, use a bigger magnet, and also move the magnet faster

Then we use this equipment in the photo to see what will happen

Then in this photo, we draw the graph of force, magnetic field. When the north pole of the magnet is going toward a loop, the flux increases and an upward secondary magnetic field is created causing a counterclockwise current. The changing flux created by the magnetic field created by the induced emf causes the the loop to float due to the force upward.

In these two photos, we first find the E that created by the moving of magnet and draw the two graphs of B and E

Summary:

     In today’s class, we learned Lenz's Law and Faraday's Law to see how we could induce a current using magnetic fields and magnetic fields, forces, torque, and flux. find that an EMF and flux explains the relationship between the two by using Lenz's law and Faraday's Law to magnetic fields. We did many experiments that made a steel ring and we saw that the forces of the magnetic field create some objects to levitate just like the rings.

Magnetism, Electricity and Motor(0512)

Magnetism, Electricity and Motor

We predict two ways to destroy a magnet. one is heating and another is hitting it.

Heating up

In this photo, we begin to do another exercise, make the loop galvanical and give it a magnet field, the direction is upward. Then we find that only the top and bottom lines has Force and the net force is 0.

Then we use the equation torque=F*r ,and F=BIL to find the torque=1/2BIL^2, and the net torque is BIL

This question is a little tricky. Theta is actually the angle between the normal vector B and the the plane, therefore the angle we used would we 90-theta, not theta.

This picture is the inside of motor.

Our demonstration of right hand rule. Notice that the thumb points in the direction of the current.

The above 2 pictures are from an experiment we did if we had a current going through the metal pole in the center of a box surrounded by compasses. We found that the current produces a magnetic field causing the magnets to point in a counter-clockwise direction around the metal pole. This matches our right hand rule along a current.

We equated two equations F=qE=qV_d xB (recall that V_d is drift velocity). We then find the current by using the drift velocity formula we had learned before to find the V_H

Here we  were tryiing to find the magnetic at the specific points inside the loop. The dots described the fingers are coming out, and the crosses described the fingers are coming in.

Universal constants given is epsilon_not and u-not. Interestingly, F_B/F_E is v^2/c^2. Therefore, if the object approached speed of light, the magnetic force and the electric force would be the same.

This is the video we made and shows the success of this small electric motor.

Summary:

     In today’s class, we learned a lot about magnetism and the properties that are inside the magnets and how they interact with the other.  We learned that torque is generated in a current loop in a magnetic field due to forces on the sides when there are N turns of wire. We learned about another right hand rule which shows us the direction of the magnetic field.  We learned how to create a magnet and how to destroy a magnet. We were also introduced to motors and use magnetic fields to rotate the motor. We also created a motor with a wires, paper clips, and a battery.

Magnetic Fields and Magnetic Forces (0507)

Magnetic Fields and Magnetic Forces

In this photo, the professor put iron filings sprinkled around the magnet and we observe that there are circles from north pole to south pole

The bar was labeled N on the left and S on the right. As we observed, the magnetic fields entered the S side and exited on the N side.

On the table was a permanent magnet. Interestingly, when the magnet was taken apart into 2 separate pieces, the pieces still behaved like a magnet with north and south parts.

We imagined that the big permanent magnet was just a accumulation of many tiny magnets. Therefore, when we broke the big one into two. the pieces behaved as two separate magnets. The tiniest magnet is the atom, assumingly

The total flux of the dipole magnet is equal to poles enclosed/ constant.

We trying to find the the magnetic field, Since the field is constant, the oscilloscope only showed a single dot on the screen. 

Here we moved the magnetic bar closer to the screen in many direction. As we moving, the dot on the screen moved in different direction. We used the right hand rule if it made sense or not. The formula here is F=v cross B

Here we were trying to find the unit of B.

Here we were practicing finding the acceleration from the given information. We first found the magnetic force, since magnetic force caused the proton to move in the circle. The magnetic force was actually centripetal force. We equated qvBsintheta= ma to find a.

Right Hand Rule

Finding the r by equating the magnetic force with centripetal force.

Here we can imagine that the magnetic is in the positive j direction. Here we had to use left hand rule because the current is actually moving electrons. When the current is in negative i direction, another word, moving from right to left, The force will be up, string up. Otherwise, string would move downward.

Finding magnetic field by equating magnetic force with centripetal force. Since w= 2*pi* frequency, since r= v/w. we put that into finding B equation

We use right hand rule for proton, and left hand rule for electron.

The current was going in the counter clock wise direction. The net force would be zero in a closed loop.

The net force in the closed loop is always zero, but not the net torque.

Homework question.

Our illustration.

Summary:

     Today, in class, we learned about magnetism and its properties. We saw how the magnetic fields looks like on the magnet.  Then we learned about the right hand rule when it comes to currents and force. We also saw that current, length and magnetic field determine the force of the magnetic field. When it is given magnetic charge by being placed in a horseshoe magnet and cut into half, the magnetic charge is shown by using a compass.

Oscilloscopes and Mystery Box (0505)

Oscilloscopes and Mystery Box

We began the class introduced to a piece of equipment named Cathode Ray Tube.The Cathode Ray Tube is an electrical component in some vacuum tubes that produces a narrow, collimated electron beam that has a precise kinetic energy. 

We were asked to predict how the Cathode Ray Tube on the Oscilloscope would change based off a change in voltage from a DC supply, we said the output would be shifted upwards and were correct because the y-axis is in units of voltage and adding voltage would just increase the y-intercept.

The oscilloscope showed a straight line because the voltage source is constant (battery). Here we used the y-division is 0.5; therefore, the voltage of the battery was roughly about 1.3 V.

Here we used the current generator connected to the oscilloscope. The lines jumped up and down continuously because the current changed the direction.

Here we input 96Hz to the scope. The interval peak to peak is 5.2 with 2mS. 1/(5.2*2*10^-3) is roughly about 96Hz.

We recorded our lab work on the white board.

The image above is Blue and Black(DC)

The image above is Red and Black (AC)

The image above is from Yellow & Black (Open) and Black & Yellow (Open)

The image above is from Black & Green (DC) and Black & Blue (DC)

Summary:

     In today’s class, we learned how to use the oscilloscope. We use different electronics to measure and visualize voltage changes. We learned to how to observant and to manipulate the settings on the machine to reveal the true wave patterns on screen. We learned many things about frequency and DC/AC circuits when connecting them to the oscilloscope. We find to use oscilloscopes in order to see voltage changes and use a simple amplifier to look at how analog electronics are used as a conversion to boost a weak signal into a sound we can hear