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www.GOALias.blogspot.comThese days Miniaturecircuit breakers (MCBs)are increasingly beingused in place of fuses.These are switches whichautomatically turn offwhen current in a circuitexceeds the safe limit. Youturn them on and thecircuit is once againcomplete. Look for ISImark on MCBs also.Fig. 14.16 Miniaturecircuit breaker (MCB)Fig. 14.17 Effect of current on acompass needle14.3 M14.3 MAGNETICEFFECTOFELECTRICCURRENTActivity 14.5CAUTIONAlways, use proper fuses which havebeen specified for particularapplications, carrying ISI mark. Neveruse just any wire or strip of metal inplace of a fuse.Take the cardboard tray from inside adiscarded matchbox. Wrap an electricwire a few times around the cardboardtray. Place a small compass needleinside it. Now connect the free ends ofthis wire to an electric cell through aswitch as shown in Fig.14.17.Note the direction in which thecompass needle is pointing. Bring a barmagnet near the compass needle.Observe what happens. Now, whilewatching the compass needle carefully,move the switch to the ‘ON’ position.What do you observe? Does the compassneedle deflect? Move the switch back tothe ‘OFF’ position. Does the compassneedle come back to its initial position?Repeat the experiment a few times.What does this experiment indicate?We know that the needle of a compassis a tiny magnet, which points innorth-south direction. When we bringa magnet close to it, the needle getsdeflected. We have also seen thatFig. 14.18 Hans Christian Oersted(A.D. 1777-1851)167ELECTRICCURRENTAND ITS EFFECTS167