Topic19Magnetism-TenburyHouse话题19磁滕伯里房子.doc

Unit 8 : Magnetism1.Three sheets of material are placed between magnets and iron nails as shown in the diagram. Which of the following describe the force onthe nail for each material?leadironaluminiumAattractionattractionattractionBattractionattractionrepulsionCattractionno forceattractionDno forceno forceno forceErepulsionattractionrepulsion2.It can be deduced that a piece of metal is already a magnet ifAcopper wire is attract to itBboth ends of a compass needle are attracted to itCa magnet is attracted to itDone end of a compass needle is repelled by itEcopper wire is repelled by it.3.Which statement about magnetism is correct?AA magnet attracts small pieces of aluminiumBSteel makes a better permanent magnet than iron does.CThere is no limit to the magnetic strength of a magnet made from a steel bar.DTwo like poles always attract one another.4.Which of the following statements describes an example of induced magnetism?ATwo North poles repel each other, but a North pole attracts a South pole.BA bar magnet, swinging freely, comes to rest pointing North-SouthCA bar magnet loses its magnetism if it is repeatedly dropped.DA bar magnet attracts a piece of soft iron.EIt is hard to magnetic steel, but easy to magnetic soft iron.5.A metal bar P-Q hung by a thin thread always comes to rest with end P pointing North. Another bar X-Y of the same metal settles in no definite direction. What happens if the two bars are brought near one another?AEnd P attracts end X but repels end Y.BEnd P repels end X but attracts end Y.CEnd P neither attracts nor repels end X.DEnd P attracts end X but end Q repels end Y.EEnd P and end Q both attract end X.6.Which of the following proves that a piece of metal is already a magnet?AA magnet is attracted to it.BBoth ends of a compass needle are attracted to it.CCopper wire is attracted to it.DOne end of a compass needle is repelled by it.7.A scrap metal dealer uses a large electromagnet.Which pair of metals will it pick up?Aaluminium and brassCcopper and ironBbrass and copperDiron and steel8.In an experiment, the north pole of a bar magnet is brought close to each end of a freely suspended soft-iron rod in turn What is the result of this experiment?ABoth ends of the rod are attracted to the north pole.BBoth ends of the rod are repelled by the north poleCNeither end of the rod is attracted by the magnet.DOne end of the rod is attracted and one is repelled by the north pole.9.One end X of a metal rod attracts the N-pole of a compass needle. What does this show about the rod?AIt could be made of copper but is unmagnetisedBIt could be made of copper with S-pole at X.CIt could be made of steel but is unmagnetised.DIt could be made of steel with N-pole at X.10. Which of the following is the most effective way to demagnetise a magnetised steel needle?ADrop it on the floor.BLeave it inside a solenoid carrying direct currentCLeave it next to another strong magnet.DSlowly pull it out of a solenoid carrying alternative current11.An iron bar is placed near a magnet as shown.Which diagram correctly shows the induced magnetisation of the iron bar? 12.Which diagram shows the magnetic field pattern associated with a solenoid carrying a current in the direction indicated? 13.A small compass is placed beside a bar magnet. In which direction will the compass needle point? 14.Which of the following could be used for the needle of a plotting compass?AaluminiumCcopperEsteel BbrassDiron 15.A permanent magnet is placed on a flat horizontal surface. A plotting compass is placed on the spot shown on the diagram.In which direction will the plotting compass point? (Ignore any effect of the Earths magnetic field). 16.The diagram shows a box which has a bar magnet hidden inside it. Compasses are placed around the outside and their needles point as shown.Which diagram shows the position of the magnet inside the box:17.It is sometimes necessary to protect electrical apparatus from magnetic field. This can be done by surrounding the apparatus with a box made from:A alumimiumB ironC rubberD steel18.Diagram 1 shows the magnetic field pattern near a bar magnet and an object XY. Diagram 2 shows the pattern that is obtained when XY is turned roundWhat is XY?Aa copper rodBa magnet with the N pole at XCa magnet with the N pole at YDa rod of soft iron19.The diagram shows a short length of iron placed near the N pole of a magnet. Which diagram best represents the resulting magnet field pattern?20.A diagram shows a sheet X of material used to provide magnetic shielding for a sensitive meter near a transformer. Which material is suitable for X? A copperB glassC ironD leadE perspex 21.A small compass is lace beside a bar magnet. In which direction will the compass needle point? 22.The diagram shows an electric bell. What materials would be suitable for the parts labeled P, Q and R?PQRAbrasssoft ironspring steelBsoft ironbrasssoft ironCsoft ironsoft ironspring steelDsoft ironbrasscopperEspring steelsoft ironspring steel23.Which two materials are most likely to be used for the coil and core of an electromagnet?coilcoreAcopperairBcopperironCcoppersteelDironironEironsteel24.A coil of copper wire wrapped around a core could be used as an electro-magnet. Which of the following combinations would produce the strongest electro-magnet?number of turnscoreAfewsoft ironBfewsteelCmanycopperDmanysoft-ironEmanysteel25.Which of the following materials is correctly described? materialpropertyuseAironnot easily demagnetizedelectro-magnetBironnot easily demagnetizedpermanent magnetCironeasily demagnetizedelectro-magnet Dsteelnot easily demagnetizedelectro-magnetEsteeleasily demagnetizedpermanent magnet26.Which of the following is the best way to demagnetise a magnetized steel needle?ABreak it into two pieces.BMake it red-hot and then let it cool.CLeave it next to another strong magnet.DLeave it inside a solenoid carrying direct current.ESlowly pull it out of a solenoid carrying alternating current.27.Three specimens of magnetic material were tested using the apparatus shown in the diagram. When the switch is closed, the specimen picks up some of the iron nails but when the switch is opened, many or most of the nails fall off. The number of nails picked up and left on were found for the three specimens. The table shows the results.specimenNo. of nailspicked upNo. of nailsleft onX354Y2010Z403What can be deduced from these results?AX would make the best electromagnet.BX would make the best permanent magnet.CY would make the best electromagnet.DZ would make the best electromagnet.EZ would make the best permanent magnet.28.Which of the following method of magnetising a steel rod will produce the strongest magnet?Abringing a permanent magnet near to the rod.Bholding heated rod in N-S direction and tapping strongly.Cpassing an electric current through the rod.Dplacing rod in a solenoid carrying a large direct currentEstroking the rod with a permanent magnet.29.In which device is a permanent magnet used?Aan electric bell Da relayBan electromagnetE a transformerCa plotting compass30.Iron and steel cylinders can both be magnetized by placing them inside a solenoid (coil) connected to a d.c. supply. Which pair of statements about the magnetic strengths of the iron and steel cylinders is correct?supply onsupply on, then offAiron strongeriron strongerBiron strongersteel strongerCsteel strongeriron strongerDsteel strongersteel stronger31.Three bars of metal are known to be brass, iron and steel. A magnet is placed at one end of each metal bar. The diagram shows how many tacks are picked up by each metal bar. What are metals 1, 2 and 3 ?Metal 1Metal 2Metal 3AironbrasssteelBironsteelbrassCsteelbrassironDsteelironbrass32.Recorded audiotapes should not be left near the back of a working television set because they could be damaged by:Ahigh-energy electronsBhigh-energy X-raysCstrong electric fieldDstrong magnetic field.33.A length of copper wire, coiled around a core, is used as an electromagnet. Which combination produces the strongest electromagnet?Number of turnsCoreAfewsoft-ironBfewsteelCmanycopperDmanysoft-iron34.In experiments with a vertically held bar magnet, its ability to attract soft iron tacks was tested. The results are shown by the diagram below. In the various cases, the average number of tacks attracted was as follows;N pole of magnet, 10 tacksN pole of magnet covered by a piece of soft iron, 8 tacksN pole of magnet covered by a piece of wood, 3 tacksa) What happened to the soft iron as it was placed in contact with the magnet?b) Suggest why the magnet covered by the soft iron picked up almost as many tacks as the magnet alone.c) If the soft iron was gently slid off the end of the magnet whilst holding 8 tacks, state and explain what would happen.d) Although wood is a non-magnet material, a few tacks are attracted when the wood is held covering the end of the magnet. Suggest a reason for this.35.The diagrams in the figure show the region between the poles. In (b) there is a piece of copper between the poles, and in (c) there is a block of soft iron. Sketch the magnetic field line patterns on each diagram. 36.Two magnets A and B are placed with their poles as shown in the next figure. a) Draw arrows to show the directions of the forces exerted on the north pole of magnet A by each of the poles of magnet B.b) Draw arrows to show the directions of the corresponding forces exerted on the south pole of B by each of the poles of A.c) Draw an arrow to show the direction of the resultant force exerted by magnet B on magnet A. Label the arrow with the letter R.d) Explain why the resultant force acts in the direction you have shown in c).37.The diagram shows the arrangement of a magnetic catch on a wooden door. a) Describe what takes place as the magnet in the door approaches the soft iron in the frame.b) Why is soft iron used rather than copper?c) State one advantage of using a magnetic catch rather than a mechanical one.38.a) The figure shows a bar magnet and four circles which represent four positions for a plotting compass. Inside each circle draw an arrow to show which way the compass needle would point. b) The next figure is a diagram of a uniform magnetic field. A soft- iron ring is placed in the field. Complete the field lines in the above figure to show the effect of the soft-iron ring on the magnetic field pattern.39.The diagram shows a two-piece device designed for cleaning both sides of a windowpane at the same time. When part A is moved over the inside surface, part B follows it, moving over the outside surface. a) Explain why(i) B follows the movement of A(ii) there is a practical limit to the thickness of the window glass for which the device works.b)When A and B are placed on opposite sides of a vertical sheet of iron, B remains where it is even when A is remove. (Suggest a reason for this)40.The diagram shows the essential features of a device used to remove magnetic objects from a mixture moving past on a conveyor belt. Switch S is closed during collection; the arm is then swung over to a container and the switch opened to deposit the co