Physical Science Past Paper PDF - Electromagnetism

PHYSICAL SCIENCE QUARTER 4 – WEEK5 ELECTROMAGNETISM BEVERLY L. GARCIA Subject Teacher MOST ESSENTIAL LEARNING COMPETENCIES 1. Describe how Hertz produced radio pulses (S11/12PS-IVf-68) 2. Explain how special relativity resolved the conflict be...

PHYSICAL SCIENCE QUARTER 4 – WEEK5 ELECTROMAGNETISM BEVERLY L. GARCIA Subject Teacher MOST ESSENTIAL LEARNING COMPETENCIES 1. Describe how Hertz produced radio pulses (S11/12PS-IVf-68) 2. Explain how special relativity resolved the conflict between Newtonian mechanics and Maxwell’s electromagnetic theory (S11/12PS-IVi-68); Electromagnetic Induction and Electromagnetic Waves What is electromagnetism? Dictionaries defined electromagnetism as a subdivision of physics that is concerned with the study of the interacting relationship of electric currents or fields and magnetic fields. What is the theory of electromagnetism? Before Maxwell pointed out the interrelationship of electric current, magnetic field and light, it is thought that the two fields and the light were once separate forces. When Maxwell studied these, he projected that the electric field, magnetic field, and light are different appearances of the same phenomenon. What are Radio waves? Radio waves, as defined by dictionaries, are electromagnetic waves. It is measured to have the longest wavelength in the electromagnetic spectrum. Contribution of Michael Faraday Induction is the process in which a magnetic field can cause a current to flow. Michael Faraday (1791–1867) came up with what we now know as the Faraday’s law of induction, which establishes how continuous change in the magnetic field induces electric field. Michael Faraday Faraday’s Law Faraday’s law can be demonstrated by having a conductor enclose an area (or in case or solenoid conductors, a stack of areas) and a magnet moving back and forth through the solenoid. You will observe the current flowing through the conductor, indicating the presence of electric field. Other ways a current can be induced are by moving the conductor or by rotating either the The faster motion of magnet in and out of the conductor or the magnets. coil yields a stronger alternating voltage. Contribution of James Clerk Maxwell Maxwell used the works of Faraday and Ampère, together with that of Carl Friedrich Gauss (1777–1855), to come up with four Maxwell’s equations that explain the relationship between electricity, magnetism, and light. Carl Friedrich Gauss Maxwell’s Equation From the four equations, Maxwell deduced the following: 1. Changing electric field induces magnetic field (e.g., in electric currents, the electric field at a point near the conductor fluctuates as the electrons come and go). 2. Changing magnetic field induces an electric field (e.g., magnetic field lines through an area enclosed by a conductor). 3. Changing electric fields and magnetic fields can mutually induce each other, causing them to propagate at a speed of in the form of electromagnetic waves. Contribution of Heinrich Hertz Heinrich Hertz (1857–1894), using Maxwell’s equations, created a device wherein a fluctuating electric current produces radio wave impulse. Radio waves are the electromagnetic waves with the longest wavelength outside the visible light range. Thus, you cannot see them, but they can Heinrich Hertz be useful in transmitting signals. Contribution of Heinrich Hertz The apparatus used by Hertz to generate and detect a radio wave. The material at the left side is an induction coil which will produce sparks between two brass balls attached to capacitor plates. On the other side of the setup is a bent loop of wire with a small gap. Contribution of Heinrich Hertz A significant observation in this experiment is the production of the secondary spark in the bent loop of wire as it is placed near the sparking induction coil. The secondary sparks are produced even if a source of electric current is not connected to it and even if the loop has no physical contact to the induction coil. This proves that the sparks across the gap of the bent loop of wire are induced because the sparks across the induction coil emitted invisible electromagnetic waves. Contribution of Heinrich Hertz The strength and rate of fluctuation of current can transmit radio pulse with intensity and different wavelengths. The radio pulse can be picked up by a similar device and convert it back to electric current with the same strength and rate of fluctuation as the original. This device by Hertz is the antenna, used in televisions and radio. Later on, he was able to calculate the speed of the radio waves he created and found that its speed is the same with the speed of light. It was through this experiment that the unit for frequency was named after him.  Michael Faraday came up with what we now know as the Faraday’s law of induction, which establishes how 1 continuous change in the magnetic field induced electric field. Maxwell’s four equations explain the relationship between 2 electricity, magnetism, and light. Heinrich Hertz, using Maxwell’s equations, created a 3 device wherein a fluctuating electric current produces radio wave impulse. Special Theory of Relativity The Theories In 1865, James Clerk Maxwell theorized that electromagnetic field moves through space at a fixed speed. He wrote set of four equations that describe all the laws of electricity and magnetism. Upon evaluating Maxwell’s equation for the speed of light, c is equal to 2.99792458✕10​8 m/s. This showed that the speed of electromagnetic waves is universal. The Theories The Special Theory of Relativity was coined and developed by Albert Einstein in 1905 as an answer to the long-debated conflict between James Clerk Maxwell’s Theory of Electromagnetism and Isaac Newton’s Three Laws of Motion.  Newtonian Mechanics Newtonian mechanics is grounded on the use of Newton’s three laws of motion. The mechanics explains that space (distance), time, and mass, are absolute. This means that the distance between two objects and the time that passes between two events does not depend on the environment where the object is in. Furthermore, according to Newton’s second law, objects in the environment moves in a straight line; hence, the change of location from one environment to another environment must register a straight line to other straight lines. Moreover, it is said that no matter where you are or how fast you are moving, there will be no changes in space or time. In all places, a kilometer is a kilometer and a minute is a minute. And you can travel as fast as you want, with adequate acceleration. Maxwell’s Electromagnetic Theory of Light James Clerk Maxwell had predicted that the electric field, magnetic field, and light are different representations of the same phenomena or event. He further predicted that visible lights are electromagnetic waves that move in a manner like ripples in the water when a stone is dropped. According to Maxwell, light as a wave have both electrical and magnetic components and that it moves at a constant speed of 186,000 miles per second. It means that the speed of light is the same for everything and for all observers The CONFLICT There is only one conflict between the two theories: according to Maxwell, light in a vacuum moves at 186,000 miles per second. And it does not change for all observers and situation. However, according to Newtonian physics, all speeds are relative – meaning speed depend on the observers, viewpoint and situation. Resolution: Einstein and the Special Theory of Relativity In 1905, Albert Einstein published his observation about the differing ideas of the two theories through the special theory of relativity. His theory is based on the observations of events from different viewpoints. He stressed that while Newtonian physics is true, Maxwell’s theory is also correct. He resolved the opposing ideas by establishing the two foundations of the special theory of relativity. Resolution: Einstein and the Special Theory of Relativity The first principle in Einstein theory is the consistent law principle. It states that all motions are relative to the selected reference frame or viewpoint. It means that the motion of an object is based on the observers’ viewpoint. First Principle: Consistent Law Example A teenage boy is standing inside a train that is passing equally between two oak trees. Because the train is moving, he saw that a lightning struck the tree on his left first then the tree on the right. Another boy, who is standing at a train platform, also saw the same event. Only, in his viewpoint, the lightning struck both trees at the same time. Resolution: Einstein and the Special Theory of Relativity The second principle in Einstein’s theory deals with the speed of light. This is the constancy of speed. He established that light moves in a speed of 186,000 miles per second and is the same for all observers’ viewpoint. Second Principle: Constancy of Speed Example An astronaut that is moving towards the source of light will think that light is moving at 186,000 miles per second. Hence, an astronaut that is not moving towards the source of light will think that light is moving at 186,000 miles per second. In short, regardless of the rate movement of the source of light and the rate movement of the astronauts, the speed of light will remain the same Einstein and the Special Theory of Relativity These two postulates clarify that if two events happen at different places, it is not always likely to say which of the two events happens first or that they occur at the same time.