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1, TECH Malappuram (Teacher Empowerment through Co-operation and mutual Help), , Unit summary note, Std 7, Unit-5, When current flows, Prepared by ILLIAS PERIMBALAM, GBHSS Manjeri, Mob : 9745200510, , Difficulties we face if no power supply, , , , , , , , We cannot read or write at night, We will have to suffer heat since instruments like fan, AC, air cooler etc will not work, We cannot pump water to tank using motor, We cannot grind the soaked rice to make breakfast, We cannot iron dresses, We cannot wash cloths using washing machine, , Circuit, If an electric instrument is connected to a power supply using wires, in such a way that the instrument works is called a circuit., , Closed and open circuit, , A circuit in which all the connections are in proper way so that the instrument in it works is called a, closed circuit. A circuit in which any part is disconnected is an open circuit. In an open circuit, the, instrument will not work., To see a video on this topic, click on the following link, https://www.youtube.com/watch?v=eUCRFeeyaII&list=PL9AshZEiXvDnIMJYqM2ECAXxrw7Dx6PvR&index=1, ]mT`mK§fpsS IqSp-X ]n.-Un.-F-^v. ^b-ep-Ifpw hoUn-tbm-Ifpw e`n-¡m³ TECH Malappuram imkv{Xm-[ym]I Iq«mbva hnI-kn-¸n¨ imkv{X-s¨¸v B¸,vt¹tÌmdn \n¶pw Uu¬temUv sNbvXv C³ÌmÄ sN¿pI., https://play.google.com/store/apps/details?id=com.basith.sasthracheppuapp.

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2, TECH Malappuram (Teacher Empowerment through Co-operation and mutual Help), , Some simple circuits, Source of electricity, Circuit -1, Circuit-2, Circuit-3, Circuit-4, Circuit -5, , Torch cells, Toy battery, Toy battery, AC power supply from a plug, UPS battery, , Electric device, Bulb, Buzzer, Mini motor, Iron box, Computer, , The wire used for, connection, Copper, Aluminum, Copper, Copper, Copper, , Essential components of a circuit, , , , , Source of electricity, Device that use electricity, Wire that conducts electricity, , Some electric circuits are given below. None of the bulbs in these circuits is glowing. Identify its, reason and note it down., , In the first circuit, the connecting wire is broken at a place. In the second circuit, the cells are not, touching each other. In the third circuit, one end of the connecting wire is detached from the, battery. Thus all the three circuits are open. So the bulbs are not glowing., , For current to flow, Make an arrangement as shown below and try to, complete the circuit using different materials. Which, materials made the bulb glow?, , ]mT`mK§fpsS IqSp-X ]n.-Un.-F-^v. ^b-ep-Ifpw hoUn-tbm-Ifpw e`n-¡m³ TECH Malappuram imkv{Xm-[ym]I Iq«mbva hnI-kn-¸n¨ imkv{X-s¨¸v B¸,vt¹tÌmdn \n¶pw Uu¬temUv sNbvXv C³ÌmÄ sN¿pI., https://play.google.com/store/apps/details?id=com.basith.sasthracheppuapp.

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3, TECH Malappuram (Teacher Empowerment through Co-operation and mutual Help), , Materials used for experiment, , Bulb glows/Does not glow, , Current is conducted/ not conducted, , Nail, Piece of paper, Block of wood, Steel spoon, Plastic wire, Rubber band, Tin sheet, Glass, Pencil core (Graphite), Copper wire, Piece of cloth, Aluminium strip, Siver ornament, Gold bangle, PVC pipe, Iron wire, , Bulb glows, Bulb does not glow, Bulb does not glow, Bulb glows, Bulb does not glow, Bulb does not glow, Bulb glows, Bulb does not glow, Bulb glows, Bulb glows, Bulb does not glow, Bulb glows, Bulb glows, Bulb glows, Bulb does not glow, Bulb glows, , Current is conducted, Current is not conducted, Current is not conducted, Current is conducted, Current is not conducted, Current is not conducted, Current is conducted, Current is not conducted, Current is conducted, Current is conducted, Current is not conducted, Current is conducted, Current is conducted, Current is conducted, Current is not conducted, Current is conducted, , Inference, Some substances conduct electricity and some not. Metals are good conductors of electricity., However, some nonmetallic substances like graphite also conduct electricity., , Conductors and insulators, Substances that conduct electricity are called conductors. Eg: - Steel, aluminium, copper, graphite,, gold, silver, tin, iron etc. Substances which do not conduct electricity are called insulators. Eg: Plastic, paper, cloth, rubber, wooden block, glass etc., To see thee interesting experiments on the above topic, click on the following links, https://www.youtube.com/watch?v=og8JRkc4Pug&list=PL9AshZEiXvDnIMJYqM2ECAXxrw7Dx6PvR&index=2, https://www.youtube.com/watch?v=PZfCaDFPwe8&list=PL9AshZEiXvDnIMJYqM2ECAXxrw7Dx6PvR&index=3, https://www.youtube.com/watch?v=b5T07o9j_Kc&list=PL9AshZEiXvDnIMJYqM2ECAXxrw7Dx6PvR&index=9, , ]mT`mK§fpsS IqSp-X ]n.-Un.-F-^v. ^b-ep-Ifpw hoUn-tbm-Ifpw e`n-¡m³ TECH Malappuram imkv{Xm-[ym]I Iq«mbva hnI-kn-¸n¨ imkv{X-s¨¸v B¸,vt¹tÌmdn \n¶pw Uu¬temUv sNbvXv C³ÌmÄ sN¿pI., https://play.google.com/store/apps/details?id=com.basith.sasthracheppuapp.

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4, TECH Malappuram (Teacher Empowerment through Co-operation and mutual Help), , Symbols used to represent components of a circuit, , Observe the following diagram. Write what is, indicated by 1, 2, 3 and 4 in this circuit diagram?, 1-Glowing bulb, 2- Conducting wire, 3-Battery, 4-Switch, , Is the circuit closed or open? Justify your answer, Since the bulb is glowing, we can understand that the circuit is closed., What change should be made in the circuit to show it as an open circuit?, We can change the switch to off mode or disconnect the connecting wire from the battery or from, the bulb for making this circuit diagram open. We can also leave a gap between the cells or break the, wire at somewhere. In all these cases, the bulb should be changed to not glowing mode., , ]mT`mK§fpsS IqSp-X ]n.-Un.-F-^v. ^b-ep-Ifpw hoUn-tbm-Ifpw e`n-¡m³ TECH Malappuram imkv{Xm-[ym]I Iq«mbva hnI-kn-¸n¨ imkv{X-s¨¸v B¸,vt¹tÌmdn \n¶pw Uu¬temUv sNbvXv C³ÌmÄ sN¿pI., https://play.google.com/store/apps/details?id=com.basith.sasthracheppuapp.

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5, TECH Malappuram (Teacher Empowerment through Co-operation and mutual Help), , Safety fuse, Safety fuse is a device used in circuits as a precaution to protect the circuit and electric devices from, damage caused by the flow of excess current., To see an experiment related with the function of fuse, click on the following link., https://www.youtube.com/watch?v=CaM6KVoUEhw&list=PL9AshZEiXvDnIMJYqM2ECAXxrw7Dx6PvR&index=4, , Is it advisable to use thick wire as fuse wire to prevent it from melting frequently?, No. If we are using thick wire for tying fuse, it won’t melt when excess electricity flows through the, circuit. So it will not save the circuit and the devices in it., , Magnet and electricity, Arrange an electric circuit and keep it switched off. Bring a, pivoted magnetic needle just below the copper wire. Observe the, direction of the magnetic needle. Now switch on the circuit and, observe the magnetic needle., Observation, On passing electricity through the wire, the magnetic needle, moves., Inference, On passing current, a magnetic field is produced around the conducting wire. It is the influence of, this magnetic field caused the movement of the magnetic needle., To see the experiment on this topic, click on the following link, https://www.youtube.com/watch?v=733RtOiJpho&list=PL9AshZEiXvDnIMJYqM2ECAXxrw7Dx6PvR&index=8, , Oersted’s principle, The scientist Christian Oersted discovered that a magnetic field is produced around a currentcarrying conductor. The is known as Oersted’s principle. Electromagnets are made by utilising the, relationship between electricity and magnetism., , ]mT`mK§fpsS IqSp-X ]n.-Un.-F-^v. ^b-ep-Ifpw hoUn-tbm-Ifpw e`n-¡m³ TECH Malappuram imkv{Xm-[ym]I Iq«mbva hnI-kn-¸n¨ imkv{X-s¨¸v B¸,vt¹tÌmdn \n¶pw Uu¬temUv sNbvXv C³ÌmÄ sN¿pI., https://play.google.com/store/apps/details?id=com.basith.sasthracheppuapp.

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6, TECH Malappuram (Teacher Empowerment through Co-operation and mutual Help), , How can we make an electromagnet?, Take an insulated copper wire of 75 cm length. Wind it closely over an iron nail from one end to the, other. Remove the insulation from both ends of the wire and connect them to a battery. Bring some, pins near the nail. They will be attracted to the nail. Here the nail becomes a magnet temporarily., Things to do to increase the power of an electromagnet, ,  Increase the number of turns of the copper wire,  Increase the intensity of the current,  Increase the thickness of the iron nail, To see two experiment related with this topic, click on the following links, https://www.youtube.com/watch?v=cRIcBjJC33E&list=PL9AshZEiXvDnIMJYqM2ECAXxrw7Dx6PvR&index=7, https://www.youtube.com/watch?v=HqXkolKdmKc&list=PL9AshZEiXvDnIMJYqM2ECAXxrw7Dx6PvR&index=10, , Devices that make use of electromagnets, Electric fan, Electric bell, Electric motor, mixer grinder, washing machine, magnetic crane, To see how a motor rotates with the help of electromagnet, click on the following link, https://www.youtube.com/watch?v=7uK8ER1-wkE&list=PL9AshZEiXvDm40gC2enil5_psRPxLZ5Fm&index=1, , Hydroelectric power station, Electricity is produced making use of the energy of the water stored in dams. The water stored at a, height in a dam is made to flow through penstock pipes to reach the turbine installed at a very low, level. The turbine rotates using the energy of flowing water. It makes the generator work and, generates electricity., To see interesting experiments on this topic, click on the following links, https://www.youtube.com/watch?v=jjZvyw-bAAU&list=PL9AshZEiXvDnIMJYqM2ECAXxrw7Dx6PvR&index=5, https://www.youtube.com/watch?v=U9hObjSeDEU&list=PL9AshZEiXvDnIMJYqM2ECAXxrw7Dx6PvR&index=6, https://www.youtube.com/watch?v=E3rpLnEerDc&list=PL9AshZEiXvDmRkmFK7oTXY8DLQwU_C46N&index=7, , ]mT`mK§fpsS IqSp-X ]n.-Un.-F-^v. ^b-ep-Ifpw hoUn-tbm-Ifpw e`n-¡m³ TECH Malappuram imkv{Xm-[ym]I Iq«mbva hnI-kn-¸n¨ imkv{X-s¨¸v B¸,vt¹tÌmdn \n¶pw Uu¬temUv sNbvXv C³ÌmÄ sN¿pI., https://play.google.com/store/apps/details?id=com.basith.sasthracheppuapp.

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7, TECH Malappuram (Teacher Empowerment through Co-operation and mutual Help), , Situations when electricity is wasted, , , , , , , , , Bulb and fan are switched on even when there is no one in the room, TV is switched on even when there is no one to watch it, Bulbs are switched on even during day time, Refrigerator is left open, Ironing dresses of the different persons of the house at different times, The pins of TV, AC, etc are kept always in the power plug which is switched on and the, operations are made only by remote controller., , Steps to avoid wastage of electricity, , , , , , , , , , , , Switch off the electric devices such as bulbs, fan, TV, AC etc when there is no one to use them, Open the doors and windows of rooms for getting light during day time instead of using bulbs, Use LED bulbs instead of filament bulbs, Use electric appliances with maximum star rate, Iron the dresses of all the family members at the same time, Do not open the door of refrigerators without need., Switch off the power plugs of AC, TV etc using switch instead of using remote controllers., Remove the unwanted mobile chargers from the plugs, Avoid unnecessary indicators in the circuit, Change very old electric appliances with new ones, , Situations of getting electric shock, , , , , , , , , While operating a switch with a wet hand, While inserting or removing plug pins when the switch is on, While using wires without insulation, While changing bulb when the switch is on, While repairing the circuit when it is on, While using damaged instruments, From the earth wire, , ]mT`mK§fpsS IqSp-X ]n.-Un.-F-^v. ^b-ep-Ifpw hoUn-tbm-Ifpw e`n-¡m³ TECH Malappuram imkv{Xm-[ym]I Iq«mbva hnI-kn-¸n¨ imkv{X-s¨¸v B¸,vt¹tÌmdn \n¶pw Uu¬temUv sNbvXv C³ÌmÄ sN¿pI., https://play.google.com/store/apps/details?id=com.basith.sasthracheppuapp.

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9, TECH Malappuram (Teacher Empowerment through Co-operation and mutual Help), , c) The copper wire is longer than required., d) The hand is placed on the torch cell., Answer: The copper wire does not touch the cell., 2) From an experiment, it was found that copper, aluminium, iron, steel etc. are conductors of, electricity. From this, we understand that, a) Heavy materials are conductors., b) All materials are conductors., c) Metals are insulators., d) Metals are conductors., Answer : Metals are conductors., , 3) Is it during the summer or the monsoon season that load-shedding is normally implemented in, Kerala? Why?, In summer season. Because major part of the electricity consumed in Kerala is produced in, hydroelectric power stations. Without sufficient water in the dams, they can’t rotate the, turban and generate electricity., 4) What safety precautions should be taken while handling an electric iron?, , , , , , , Insert and remove the pin from the power plug only after making the plug switch off, Make sure the insulation of the conducting wire is proper, Make sure that no current is there on the external body of electric iron., Wear shoes, , ]mT`mK§fpsS IqSp-X ]n.-Un.-F-^v. ^b-ep-Ifpw hoUn-tbm-Ifpw e`n-¡m³ TECH Malappuram imkv{Xm-[ym]I Iq«mbva hnI-kn-¸n¨ imkv{X-s¨¸v B¸,vt¹tÌmdn \n¶pw Uu¬temUv sNbvXv C³ÌmÄ sN¿pI., https://play.google.com/store/apps/details?id=com.basith.sasthracheppuapp.