Electricity And Magnetism Grade 10 PDF

# ELECTRICITY AND MAGNETISM ## SCIENCE GRADE 10 - UNIT II - Electricity is produced by vibrating or flowing charges. ## What is a Magnet? - A magnet is a material that produces a magnetic field. ## What Materials are Magnetic? The following elements are magnetic: - **Iron (Fe)** - Atomic N...

# ELECTRICITY AND MAGNETISM ## SCIENCE GRADE 10 - UNIT II - Electricity is produced by vibrating or flowing charges. ## What is a Magnet? - A magnet is a material that produces a magnetic field. ## What Materials are Magnetic? The following elements are magnetic: - **Iron (Fe)** - Atomic Number: 26 - Atomic Mass: 55.85 - **Cobalt (Co)** - Atomic Number: 27 - Atomic Mass: 58.93 - **Nickel (Ni)** - Atomic Number: 28 - Atomic Mass: 58.96 - Many alloys of these metals like steel and alnico are magnetic. ## Magnetism - Magnetism is commonly attributed to ferromagnetism and electromagnetism depending on the moving charges and the material. - Every atom and all moving charges are in constant motion and therefore has a bit of magnetism due to magnetic spins and domains creating a net magnetic field. - **How it's Made - Magnets** - A diagram of an unmagnetized material shows several magnetic domains in random directions, while a magnetized material shows the magnetic domains all aligned in the same direction. - Before magnetization, domains behave randomly, and after magnetization, they align in a single direction. - A magnet has two magnetic poles (north and south seeking poles), and there are magnetic field lines around the magnet. - Magnets exert either a force of repulsion or attraction. - **Attraction:** - N-S - S-N - **Repulsion:** - N-N - S-S - If a force of attraction is possible between an object and a magnet, then the object interacting with the magnet contains a ferromagnetic substance and is considered naturally magnetic. - If a force of repulsion is also possible between an object and a magnet, then the object interacting with the magnet may also be a permanent magnet or a temporarily magnetized ferromagnetic material. - Diagrams show the magnetic field lines of attraction and repulsion. ## Which arrangement of three bar magnets results to an attraction between the first and the second, and a repulsion between the second and the third magnet? - The correct answer is **C.** ## MAGNETIC EFFECT OF A CURRENT - In 1819, Hans Christian Oersted accidentally discovered that when a current was switched on, a compass needle deflected. ## OERSTED'S EXPERIMENT - A diagram shows how the compass needle is deflected when the current is switched on. - This observation fired up tremendous research on electromagnetism. As a result, the effect on the motion of conductors placed within a magnetic field (such as in the operation of electric motors) was also experimented much and paved the way for practical electricity. - Twelve years after this discovery, Michael Faraday ('Fer-ə-dā) conducted his famous induction ring experiment showing that current can be produced by sources of changing magnetic fields. - This is the key principle to practical generation of electricity. - Many of the recording technology are founded entirely or partially on the relationship between electricity and magnetism known as **electromagnetic induction**. - **Electromagnetic induction** is a phenomenon of inducing a voltage in a conductor by changing the magnetic field near the conductor. - If a magnetic field within a closed loop changes in any way, a voltage or electromotive force is induced (produced) in the loop. - A diagram showing the inductive process. ## QUIZ ### ANSWER IN 1/8 SHEET OF PAPER ## TEST I ### Sum it Up Challenge! The process by which the screws become magnets is called **magnetic induction**. This same process is the reason why magnets **attract** non-magnetized magnetic substances such as the screw. The screw becomes **an induced** magnet with the end nearer the magnet having **an opposite** polarity to that of the permanent magnet. Hence attraction happens **after** magnetic induction occurs. ## Which arrangement of three bar magnets results to a repulsion between the first and the second, and an attraction between the second and the third magnet. - The correct answer is **C.** ## TEST II ### SCI. BOOK P 84-87 ## 1. In which case or cases is electric field present? - I. A spark jumping between two nearby rods. - II. A charge that is momentarily at rest. - III. A rotating bar magnet. - The correct answer is **a. I only** ## 2. In which case can a magnetic field be produced? - a. A charged comb. - b. A falling glass rod. - c. A welder's arc flash. - d. A rolling plastic cylinder. - The correct answer is **c. A welder's arc flash.** ## 3. Which device can be used to determine the polarity of an unmarked magnet? - a. a charged glass stirring rod - b. a gold-leaf electroscope - c. a sprinkle of iron filings - d. an improvised compass - The correct answer is **d. an improvised compass** ## 4. How will you describe the magnetic field around a straight current-carrying wire? - The magnetic field is strongest near and around the wire. - The magnetic field consists of straight lines parallel to the wire. - The magnetic field does not vary with the distance from the wire. - The magnetic field gets stronger with increasing distance from the wire - The correct answer is **a. The magnetic field is strongest near and around the wire.** ## 5. Which statement about an electromagnet is TRUE? - The electric field surrounding a battery-powered electromagnet alternates constantly. - The current in the electromagnet coil temporarily magnetizes the iron core. - The electric field strength is inversely proportional to the current. - The magnetic field lines produced are all straight. - The correct answer is **b. The current in the electromagnet coil temporarily magnetizes the iron core.** ## 6. What can be inferred from the alignment of compass needles in the set-up below? - A permanent magnet is nearby. - The power switch was turned off for long. - The current-carrying coil becomes magnetic. - There is a constant and uniform magnetic field around the coil. - The correct answer is **d. There is a constant and uniform magnetic field around the coil.** ## 7. As part of a traffic light system, large loops of wire are buried beneath road intersections. Which of the statements is NOT TRUE about the operation of this traffic light system? - Vehicles driven over the buried coils activate a traffic light sensor. - The conducting loops activate a color-dependent field. - The alternating current sent through the buried coils produce an electromagnetic field in each coil. - A minimum number of vehicles over the coils can trigger the traffic light to change green. - The correct answer is **b. The conducting loops activate a color-dependent field.** ## 8. Complete the following statement: Moving a metallic detector past a 5 peso coin creates a secondary magnetic field that is most similar to that of - a horse shoe magnet - a flat refrigerator magnet - a current-carrying, circular loop - a V-shaped straight wire that carries a current - The correct answer is **c. a current-carrying, circular loop** ## 9. During the Student Technologists and Entrepreneurs of the Philippines (STEP) Competition in Landscaping, a water pond transformer changes 216 V across the primary to 12 V across the secondary. If the secondary coil has 10 turns, how many turns does the primary coil have? - 10 turns - 18 turns - 180 turns - 228 turns - The correct answer is **c. 180 turns** ## 10. What basic principle enables ALL electric motors to operate? - Iron is the only element that is magnetic. - Opposite electric charges attract and like charges repel. - A moving conductor within a magnetic field will experience an electromotive force. - A current-carrying conductor placed within a magnetic field will experience a magnetic force. - The correct answer is **d. A current-carrying conductor placed within a magnetic field will experience a magnetic force.** ## 11. A magnet moves inside a coil. Consider the following factors: - strength of the magnet - number of turns in the coil - speed at which the magnet moves - Which can affect the electromotive force (emf) induced in the coil? - only - only - only - All three factors - The correct answer is **d. All three factors** ## 12. Which statement about transformers is FALSE? - A step-down voltage transformer steps up the current. - Transformers use mutual induction. - Transformers are an application of Faraday's and Lenz's Laws. - A transformer can function with either an alternating current (AC) or a steady direct current (DC). - The correct answer is **d. A transformer can function with either an alternating current (AC) or a steady direct current (DC).** ## 13. What is TRUE about the intercom system that is shown below? - The part A of the intercom system serves as a microphone only, while part C serves as a loudspeaker only. - Either parts A and C of the intercom when switched as such can be used as a microphone or as a loudspeaker. - The microphone part only basically consists of wires, a cone diaphragm, a magnet, and a coil. - The loudspeaker part only basically consists of wires, a cone diaphragm, a magnet, and a coil. - The correct answer is **b. Either parts A and C of the intercom when switched as such can be used as a microphone or as a loudspeaker.** ## 14. What transformation can take place in an improvised generator? - mechanical energy into electrical energy - electrical energy into mechanical energy - alternating current into direct current - direct current into alternating current - The correct answer is **a. mechanical energy into electrical energy** ## 15. A loop of conductor lies flat on a horizontal table. A toy magnet is hanging still over it with the magnet’s north-seeking pole pointing down. What happens next? - The magnet produces a clockwise current in the coil. - The magnet does not produce any current in the coil. - The magnet produces an upward electromagnetic current. - The magnet produces a counterclockwise current in the coil. - The correct answer is **b. The magnet does not produce any current in the coil.** ## ANSWER ### Sum it Up Challenge! The process by which the screws become magnets is called **magnetic induction**. This same process is the reason why magnets **attract** non-magnetized magnetic substances such as the screw. The screw becomes **an induced** magnet with the end nearer the magnet having **an opposite** polarity to that of the permanent magnet. Hence attraction happens **after** magnetic induction occurs.