An RLC circuit is set up in this part. The theoretical resonance frequency is solved for using values of the inductor and capacitor found with the multimeter. The experimental resonance frequency is found by using the function generator.
For part two, the experimental impedance is found with the measured values from the multimeter and the formula Z=sqrt((R^2 + (Xl-Xc)^2). That value is then compared to the theoretical value of impedance; Z=R.
For part three, the theoretical frequency and experimental frequency can be found using LoggerPro.
Lab Set UP
Result Tables
As we can see on the graph, there is a phase angle difference of 180 degrees. If the frequency increases, the amplitude decreases when measuring across the capacitor and the amplitude increases when measuring across the inductor.
Transformers
Transformer can change the voltage input and output a different voltage. It is made of two inductors linked together by an iron core. The iron core redirects magnetic flux in one inductor to the other. When there is a change in magnetic field, it creates a current. In transformers, we do not want the current because it causes energy lost. A solution to this is to laminate the plates of the metal. The lamination reduces the size of the induced loop and therefore reduces the amount of energy lost.
The picture of a transformer
Summary:
In today's lab, we learn how a transformer works. We also have more understanding of a RLC circuit.
When studying a resistor in an alternating circuit, it is connected with a function generator and multimeter (measuring current) in series. We also attach a resistor with a voltage meter.
This is the set up of the lab.
Our LoggerPro Data.
We then get the graph a Potential vs. Time, Current vs. Time, and Potential vs. Current.
Our result and percent difference.
To calculate the theoretical Irms and Vrms, the Imax and Vmax we get from the LoggerPro graphs and divided by square root 2. Using those values, we calculate the percent difference of voltage and current.
Capacitors in an Alternating Circuit
When studying a capacitor in an alternating circuit, we use same set up from the resistor one expect that we replace the resistor with a capacitor. In AC circuits, capacitors exhibit a resistance. This resistance/reactance is given by Xc= 1/(Omega)C where omega=2πf.
Lab Set Up
Our data from LoggerPro
We get data from LoggerPro. The Vmax and Imax were taken from the graphs and used in order to find the Vrms and Irms.
Using the formula for reactance, the theoretical and experimental values are found and the percent difference is calculated.
Inductors in an Alternating Circuit
For studying inductors in an alternating circuit, the same set up is used while replacing capacitor with an inductor. Using data from LoggerPro graphs, calculation of Vrms, Irms, and Xl, the experimental resistance of the inductor is calculated and the theoretical inductance is found with a volt meter. The percent difference is found to be 149.6%.
Lab Set Up (Right Side)
LoggerPro Data
Results Table
For the second part, we put a iron core and do the same steps from part 1. In the end, a 77% difference is calculated, a much lower percent difference than without the iron core. This is due to the iron core increasing the inductance without changing the resistance.
RC Circuits
For the final part of the lab, we study a RC cirtuit. A resistor and a capacitor are connected to a function generator and a current meter and volt meter with to LoggerPro. Using the graphs the Vmax and Imax are found and so are the Vrms and Irms. The total resistance within the circuit is the total impedance, or Z.
Lab Set Up
LoggerPro Data
The percent difference is found for the impedance as well as for the time phase change. Once again, using the values from the graph, The time difference for a period was found and divided by the period, 1/frequency.
Summary: Today, we talk about an AC circuit again. In AC circuit, the voltage and current varies in a sine function. We quickly reviewed DC and AC circuit and then defined formulas for I,V, Irms, Vrms, and Pavg in an AC circuit. We learn some property of resistor, capacitor, and inductor.
We study inductance by doing ActivePhysics. We answer Questions 1-8.
Measuring Inductance:
In this lab, we build a circuit with a function generator, a resistor, and an inductance. In addition, a voltage meter is used in order to find the voltage across the resistor and inductance.
Lab Set Up
The graph shows that the voltage change of the inductance.
The calculation of turns in the inductance is shown here.
Summary:
In today's lab, we introduce the topic of inductance. We derive several formulas. We learn how to calculate the turns with a oscilloscope.
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.
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.
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.
Result Tables
