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GURUKUL CENTRAL ACADMY, CH.- 13. ELECTRIC CURRENT, AND ITS EFFECTS, WORKSHEET-1, A. 1. Electric current flows from the positive terminal of the cell to, negative terminal., 2. When a bulb is connected to an electric cell through wires, it is, called a closed circuit., 3. Electric appliances such as convector, work on the principle of, heating effect of electric current., 4. A fuse is a safety device., 5. A switch helps in regulating the flow of electric current., B. battery, wires, electricity, an electric bulb, wires, switch, circuit,, electric, WORKSHEET-2, D. 1. battery, 2. solenoid, , 3. fuse, , 4. short circuit, , TEXTBOOK EXERCISES, Page 165 Try These, 1. Switch, 2. Closed circuit 3. Filaments, , EXERCISES, A. 1. d. 2. a. 3. b. 4. d. 5. b. 6. b. 7. b. 8. c. 9. d. 10. b., , 4. Electric fuse
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GURUKUL CENTRAL ACADMY, B. 1. electricity, 2. heat 3. ohms, 4. Miniature Circuit Breaker 5. Electromagnetism, 6. high, 7. metallic 8. Gong, C. 1. False, , 2. False, , 3. True, , 4. False, , 5. True, , 6. False, , 7. True, , 8. False, , D. 1., , Heating effect, 2. The unbroken path through which an electric current flows is called, an electric circuit., 3. Switch, 4. To avoid electric fire, 5. Yes, 6. MCB, 7. Cobalt and nickel, 8. Electric bell, loudspeaker, fans, , E. 1., , The electric current flowing through the filament of the bulb is, actually heating the filament. Therefore, the electric bulb feels hot., , 2., , Refer fig. 13.3 (a)., , 3., , MCB is used in place of fuse of as a safety device. It is a switch, which automatically trips down if the electric current flowing, through the circuit exceeds its limit., , 4., , The strength of an electromagnet depends upon the number of, turns of the coil around the magnetic substance. The magnitude of, electric current passing through the conducting wire also influences, the strength of the electromagnet.
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GURUKUL CENTRAL ACADMY, , F., , 5., , LED stands for Light Emitting Diodes., , 6., , When electric current passes through the wire, the needle of the, magnetic compass shows deflection., , 7., , The fuse wire is made up of a suitable alloy which has low melting, point (an alloy of lead and tin) fitted in a cartridge made up of, porcelain or glass. When electric current exceeds beyond its certain, limit, it heats the fuse wire which melts and breaks due to its low, melting point. The flow of electric current stops and the circuit, breaks., , 8., , Solenoid is a device made of a long wire that has been wound, many times into a tightly packed coil., , 1. When electric current flows through a wire or a simple conductor,, it gets heated. This effect of electric current, is known as the, heating effect of electric current. Heat produced in a conductor, depends upon the material the conductor is made of and the, resistance it offers. The lower the resistance, the greater is the, magnitude of electric current flowing. The higher the resistance, offered by the wire, the greater would be the amount of heat, generated. That is why, copper wires which offer very little, resistance, do not get heated up. Nichrome and tungsten offer high, resistance to the flow of electric current and get heated up. Heat, generated also depends upon the amount of current passing, through it., 2., , Refer Experiment 1, page 165.
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GURUKUL CENTRAL ACADMY, 3., , No.Electromagnetsareusedinnumerouselectricalappliances such as, electric motors, electric bells, loudspeakers, fans and refrigerators., Very strong electromagnets are used in cranes to pick magnetic, materials. Electromagnets are also used in hospitals for removing, iron splinters from the eyes. But electromagnets cannot be used to, separate plastic bags from the dump as plastic is not a magnetic, substance and cannot be picked up by a magnet of an, electromagnet., , 4., , When electric current passes through a conductor, a magnetic field, is created around it. This shows the magnetic effect of current. The, strength of an electromagnet depends upon the number of turns of, the coil around the magnetic substance and the magnitude of, electric current passing through the conducting wire., , 5., , Construction: An electric bell consists of an electromagnet (a coil, of wire wound on a horse-shoe iron piece), an armature, a contact, adjusting screw, a gong and a hammer. The armature consists of a, soft iron rod mounted on a spring. One end of the coil (of the, electromagnet) is connected to a contact screw through a switch, and it is joined to a source of current. The other end of the coil is, connected to the lower end of the hammer also called armature., The armature rests on the contact screw. There is a metallic gong, placed in front of the hammer. The gong is not connected anywhere, in the circuit., , Working: When the switch is ‘On’, the circuit is closed and the, electric current starts flowing from the battery through the wires, going into the electromagnet. Once the electric current flows through, the electromagnet coil, it behaves like a magnet and attracts the iron, armature and the hammer hits the gong. At the same instant, the screw, gets detached from the iron armature, breaking the electric circuit., There is no further attraction and the iron armature comes back to its, , G. 1.
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GURUKUL CENTRAL ACADMY, original position. Once it touches the screw again, the circuit becomes, closed and again the coil behaves like a magnet., , 2. Refer fig. 13.16 (a).
