Electromagnetic Induction (Faraday's Law and Lenz's Law)

The objective of the experiment is to analyze the mechanisms involved in Faraday’s law and Lenz’s law of induction and electromagnetic induction set-up.

In the experiment we made use of a galvanometer, power supply, large and small solenoid, bar magnet, aluminum metal rod and an iron rod.

     The experiment consists of four parts. In the first part of the experiment, the direction of deflection of the galvanometer was examined. It was connected to a power supply and a large resistor. For the large resistor, the human body was considered. The direction of deflection that the pointer of the galvanometer made was recorded. The current was reversed and the change in the direction of deflection was also noted.

Galvanometer

            In the second part of the experiment, the effect of magnetic flux to the induced current in a solenoid was studied with the use of galvanometer. The terminals of the solenoid were connected to a galvanometer. A bar magnet was moved in and out of the solenoid and the corresponding magnitudes displayed by the galvanometer was recorded. The speed in which the magnet was moved was increased and the corresponding magnitudes were also gathered. The other pole of the magnet was then used and analogous data were taken following the same procedures.

Bar magnet inside solenoid

            In the third part of the experiment, a small (primary) solenoid was placed inside a larger (secondary) solenoid making sure they are insulated from one another. The galvanometer was connected to the secondary solenoid while the power supply was connected to the primary one. The power supply was turned on and off and the corresponding magnitudes produced were gathered. An iron rod was placed inside the primary solenoid and the same procedures were made gathering the magnitudes produced. The iron rod was replaced by an aluminum rod and analogous data was taken following the same procedures.

Magnetic field lines of a solenoid

            In the last experiment, the same set-up from the third experiment was prepared. Inside the primary solenoid was an iron rod. The primary solenoid was pulled out of the secondary solenoid with 1cm increments taking note of the magnitude displayed in the galvanometer in every increment made. A graph of the length of the primary solenoid versus its magnitude was plotted and analyzed.

It was found out that the galvanometer responds to a change in current and reversing the current displays an opposite direction of deflection and Faraday’s law and Lenz’s law were proven true. It was confirmed that current-carrying wires produce a magnetic field and a complement of magnetic objects increases the current produced and that the number of coils in a current-carrying wire is directly proportional to the magnetic flux.

Sources of Magnetic Field

The study of magnetic field of magnets and current-carrying materials was conducted.

The experiment consists of three parts. In the first part of the experiment, the magnetic field of both the horseshoe magnet and the bar magnet was examined. The magnetic fields at different points near and on the surface of both magnets were measured and recorded using a magnetic sensor connected to LabQuest. A comparison between the data was made.

Magnetic field around a horseshoe and a bar magnet

Iron filings scattered in a sheet of paper with a horseshoe magnet underneath

Iron filings scattered in a sheet of paper with a bar magnet underneath

            The second part of the experiment aims to find out the magnetic field lines produced by a horseshoe magnet and a bar magnet. Iron filings were scattered in a sheet of paper to serve as indicators of the magnetic field lines. In one set-up, a horseshoe magnet was placed beneath the sheet of paper. Using a camera the representation of the magnetic field was recorded. A bar magnet was used on the other set-up.

            The third part of the experiment studies the magnetic field that runs through a charged coil of metal wire. The effect of the position, current and the length of the wire to the magnetic field were studied. In determining the effect of position, the coil of metal wire was stretched in to a length of one meter. Using the magnetic sensor and LabQuest the magnetic field of the coil was measured in 10cm intervals, starting from -10cm up to 120cm. To determine the effect of current, the magnetic sensor was placed 50cm from the edge of the coil. The current that runs through the coil was increased by 0.5A from 0.5A to 2.5A. The magnetic field at every 0.5A interval was recorded. To determine the effect of the length of wire to the magnetic field, the wire was compressed and stretched to a length of 25cm up to 125cm with a 25cm interval. The magnetic field at which was taken by placing the sensor in the middle of the wire.

It was found out that the magnetic field of both a horseshoe and bar magnet at one of its pole would be the same around that pole and that the magnetic field is zero at the middle of the magnet, the magnetic field lines would be the same as the electric field lines and the theory, the magnetic field that runs through a charged coil of metal wire is parabolic where the highest value is at the middle of the wire, the relationship between the current and the magnetic field is directly proportional while the relationship between the magnetic field and the length of wire is inversely proportional

Capacitors and RC Circuits

The mechanisms and properties of capacitors were examined. Three experiments were conducted: physical analysis of a capacitor through dissection, measuring the total capacitance of two capacitors arrange in series and in parallel circuits and measuring the voltage of an energized capacitor. It was found out that a capacitor is composed of a dielectric compressed by two metal plates, the total capacitance in a parallel connection is the summation of the capacitance of each capacitor present in the circuit while the total capacitance in a series connection is the inverse sum of the reciprocals of the capacitance of each capacitor and that the ability of a capacitor to be energized is a bounded exponential growth.

Capacitors

  

   The experiment consists of three parts. In the first part of the experiment, a cylindrical plate capacitor was dissected and examined. There were three fragments found inside a capacitor all of which were sketched and named.

Cross section of a capacitor

The second part of the experiment is the study of the behavior of capacitors in a circuit in series and in parallel arrangement. The group measured the capacitance of two different capacitors and arranged them first in series, then in parallel. The total capacitance of both set-ups was gathered and recorded.

The third experiment dealt with the capability of a capacitor to store energy and how much voltage runs across it through time. A circuit composed of a capacitor, power supply and a resistor was set. Five circuit combinations were made. Each one differed by an increase of the resistance which was made by adding another resistor. A voltmeter was connected to each combination for the recording of the voltages. From zero volts stored, the capacitor was energized to maximum capacity. Using a stopwatch, the increase of voltage through time in five (5) second intervals was taken. These served as points for the plot of voltage across the capacitor as a function of time. The same process was applied for all combinations.

DC Circuits and Kircchoff's Rule

This is so far the shortest experiment we had. It was just basically creating a single complex network of resistors connected to two power sources with a certain arrangement.

Schematic Diagram

          With the aid of Kirchoff’s rule we analyzed and examined the nature of DC circuits. We took the needed data and used them in the derived formula to prove our hypotheses. And in the end of the experiment, it was true enough that the theory is correct. The summation of the current into any junction is zero (junction rule)  and the algebraic sum of the potential differences in any loop, including those associated with emf’s and those of resistive elements, must equal zero (loop rule).

References:

      H.D. Young, R.A. Freedman, University Physics with Modern Physics, Pearson Education Inc., 2004.

Resistance and Ohm's Law

                   The electrical resistance of a circuit component or device is defined as the ratio of the voltage applied to the electric current which flows through it. It is a property of a component to oppose the passage of electric current. Resistors are devices which provide resistance in a circuit. Resistance, together with current and voltage, compose the Ohm’s law which shows the relationship between them. When the resistance of a material remains constant in a wide range of voltage then the material is said to be an ohmic material.

the power supply

readings

                  In this experiment, there are a number of set-ups made to study the nature of resistors and its types. Carbon film resistors, metal film resistors, ceramic resistors, resistance box and a rheostat were individually examined of their properties and function. Studies of a combination of resistors were done as well for a full grasp of the nature of resistors. The group recorded the resistance values of each device and how it affected the current when variable voltage is applied to the circuit. In doing this, sufficient information about resistors was gathered.

resistance box

          It was found out that the values of the color coded ceramic resistors are close to their actual resistance, the resistance box is a series of resistors with different strengths of opposition to current, the rheostat supplies a wide range of resistance along its length, a combination of resistors has a variable total resistance depending on the orientation of the circuit and that the electric current and voltage is directly proportional under constant resistance. 

breadboard

Electric Potential and Electric Field

      The experiment last week was kind of a challenge. Not knowing much about the experiment or about electric field lines and equipotentials is kind of a disadvantage. Our group had a difficulty finding the electric field lines and actually what we are doing is wrong. But before I go to those details I’ll introduce our activity first.

      The Title of the experiment is “Electric Potential and Electric Field”. What we are to do is to know and graph the equipotentials and electric fields of 3 set-ups: a) 2 metal disk, b) 2 line charges and c) one metal disk and one line charge. The general set-up consists of an electrolytic tank, probes, conductors, DC voltmeter and the charges. 

     Using the probes and the DC Voltmeter we looked for spots where the reading will be 0 to be able to graph the equipotentials. Unfortunately, all the way throughout the experiment we did just that. We run the probe around the electrolytic tank searching for zero-reading points. Well, it was partly correct however that should’nt have been the bulk of the experiment. We should’ve been looking for voltmeter readings which grow larger or smaller every other electric field line. For example:

Line charge and metal disk 

     As you can see, each electric field gives a different reading.

     The reading should differ from one field line to another.

    Basically that’s what we did in the experiment. Searching, gathering data, plotting points, graphing. With these, we answered the questions and finished the paper. For more of the graphs.

Line charges

Metal disks