Unit 8 Making use of electricity

1、unit 8 making use of electricity multiple-choice questions0810011.what does the following circuit symbol represent?afuse blight bulbcresistor dswitch2which of the following is the circuit symbol of a light bulb?b abcd0810033which of the following symbols represents the device that changes chemical e

2、nergy into electrical energy?b abcd4which of the following symbols represents the device that can change electrical energy into light and heat energy?b abcd5what is the voltage of four 1.5 v cells joined in series?a1.5 vb3 vc4.5 vd6 v0810066which of the following materials does not conduct electrici

3、ty?agoldbironcmercurydrubber0810077which of the following materials is an insulator of electricity?arustbcoppercirondgold0810088study the ammeter readings below. how much current does the wire carry?given 1 a = 1000 maa73 ma = 0.073 ab76 ma = 0.076 ac(0.08 a + 76 ma) / 2 = 0.078 a d0.08 a0810099whic

4、h of the following is a proper arrangement of an ammeter? ab cd 08101010which of the following is a proper arrangement for measuring the voltage across the light bulb?abcd08101111metals are good conductors. the following table shows how well several metals conduct electricity.metalability to conduct

5、 electricityaluminium370copper580iron100silver620which of the following is the best conductor?a. aluminiumb. ironc.silverd. copper 08101212which of the following circuits is the odd one?ab cd08101313which of the following diagrams best describes the headlamp circuit of a car?headlamp rheadlamp llrrl

6、rlrlabcd 08101414two identical resistors are connected in series. if the current flowing through point x is 0.1 a, what is the current flowing through point y?yx0.1 aa0.05 ab0.1 ac0.2 ad0.4 a08101515bulbs x, y and z are in series. if bulb x burns out, what happens to bulb y and z?zyxathey stop glowi

7、ng.bthey glow dimmer.cthey glow brighter.dunaffected. they glow in the same brightness.08101608101716which resistor in the following circuit draws the largest current?z30 wy20 wx10 waxbyczdall are the same08101817what is the current that passes through bulb x?0.1 ayx0.3 aa0.1 ab0.2 ac0.3 adcannot be

8、 determined08101918light bulbs x and y are identical. how much current passes through the light bulbs?xy0.1 a3 vbulb xbulb ya0.1 a0.1 ab0.05 a0.1 ac0.1 a0.05 ad0.05 a0.05 a 08102008102319the four wires, each made of different metals, are of the same diameter and length. their resistance is shown in

9、the following table. which wire is the best conductor among them?wireresistance (w)a0.01b0.012c0.018d0.0208102420normally every wire has a resistance, though very small. this causes an energy loss during transfer, as electrical energy changes intoasound energy.bheat energy.cpotential energy.dchemica

10、l energy. 081025well done, girls! you have finished 20 mc. please check your answer below.1234567891011121314151617181920dadaddabaacdabaabaab21which of the following quantities is measured in the unit w?acurrentbpowercresistancedvoltage08102822which of the following devices make(s) use of the heatin

11、g effect of current?(1)toaster(2)heater(3)fan(4)radioa(1) and (2) onlyb(1) and (3) onlyc(2) and (3) onlyd(2) and (4) only08103023which of the following descriptions is/are true for a fuse?(1)it is made of a low-melting-point wire.(2)it blows out when the current is larger than its rating. (3)its cir

12、cuit symbol is a(1) and (2) onlyb(1) and (3) onlyc(2) and (3) onlyd(1), (2) and (3)08103124which of the following symbols represent the device that can protect electrical appliances from damage by a large sudden current? abcd08103225which of following is a safety device that can cut off the electric

13、ity when the current is too large?aammeterbcircuit breakerc rheostatdvoltmeter08103326label the pins in the following diagram.yzxyzaliveearthneutralbliveneutralearthcearthliveneutraldneutralliveearth 081034answers for multiple choice (q 21 to q 26)21. c 22. a 23. d 24. b 25. b 26. clabel the holes x

14、, y and z.xzyxyz aliveearthneutral bliveneutralearth cearthliveneutraldearthneutral lived081035what is the use of the earth wire in an electrical appliance?ato protect us from an electric shockbto direct current to earth when we switch on the appliancecto supply electricity to the electrical applian

15、cedto reduce the current loading by sharing the current with the neutral wirea081036which of the following is a short circuit?abcdb081037ewhich of the following bulbs draws the largest current?a100 w bulb operating at 220 v b60 w bulb operating at 220 vc250 w bulb operating at 110 v (american standa

16、rd)d100 w bulb operating at 110 v (american standard)c081038eif a bulb is operating at 20 v and 0.1 a, how much energy is being used for 1 hour?a200 jb2000 jc3600 j d7200 jd081039eif the cost of electricity is $1 for 1 kilowatt-hour, what is the cost of using a 100 w lamp for half an hour?a$0.05b$0.

17、5c$1d$1.5a081040ewhich of the following devices does not make use of an electromagnet?aelectric bellbloudspeakercelectric motordelectric iron d081101which of the following is a closed circuit when we press the switch?abcdb081102which of the following materials is a conductor of electricity?aglassbpl

18、asticcwooddcopperd081103which of the following circuit diagrams best represents the set-up below?abcdd081104if the reading of the voltmeter is 1.5 v, what is the voltage across resistor x in the following circuit? a0.75 vb1.5 vc3 v d4.5 vb081105consider the plug below which of the following best des

19、cribes the mistake made in the arrangement?athe plug does not need a earth wire.bthe plug should not have a fuse.cthe live wire and the earth wire are in wrong position.dthe neutral wire and the live wire are in wrong position.c081106ewhat is the power of an electrical appliance at 220 v, 0.4 a?a22

20、wb44 wc88 w d220 wcb true or false questions082041if the electric particles flow faster along the circuit, it gives a largercurrent.t082042in a series circuit, the current is the same at every point.t082043in a series circuit, the voltage is the same at every point.f082044in a parallel circuit, the

21、current in the main loop is equal to those in the branches.f082045a fuse can protect electrical appliances from damage by a large current,as well as our lives,.t082046the current flows through a short circuit is larger, because the distance itravels becomes shorter.f082047the colour of the live wire

22、 is red and green.f082048ea 100 w light bulb draws a larger current than a 50 w one at the samevoltage.t082049ethe magnetic effect of current directly depends on the voltage applied.f082050eputting a soft iron bar into the core makes an electromagnet stronger.t082107in everyday lives, every device h

23、as a resistance, therefore current stops if we take away the voltage across it.t082108if a battery has a higher voltage, it delivers more electric particles in thecircuit.f082109under normal condition, the earth wire does not carry any electriccurrent.t082110the mains voltage in hong kong is 110 v.f

24、082111ea 100 w light bulb is brighter than a 50 w light bulb because it changesmore electrical energy to light in one second.t 082112ecurrent produces a magnetic effect. this means a current-carrying wireor solenoid can affects the direction of a compass needle.t082113the colour of the neutral wire

25、is blue.tc fill-in-the-blanks083051when a light bulb is turned on, electric charges are pushed to flow through it. the flow of the electric charges are called , and the path they flow along is called a(n) .current, circuit083052when the switch is turned off, the circuit is incomplete and is said to

26、be a(n) circuit. when the switch is turned on, the circuit is complete and is said to be a(n) circuit.open, closed083053we draw diagrams with symbols that represent the electrical components. such diagram is called a .circuit diagram083054a(n) is a material that contains movable charges; therefore e

27、lectric current appears in such materials when voltage is applied.conductors083055a(n) is a material that does not contain movable charges; therefore no electric current appears in such materials when voltage is applied.insulators083056the electrical energy given to each unit of electric charge is c

28、alled . its unit is .voltage, volt083057the unit of electric current is . it is measured with a kind of meter called .ampere, ammeter083058the current flowing through every electrical component is the same in a circuit, where an electric charge having a round trip will pass through all components.se

29、ries083059an ammeter is connected up in to a device to measure the .series, current083060a voltmeter is connected in to measure the applied to a component in a circuit.parallel, voltage083061 is the opposition to the flow of the electric charges. its unit is .resistance, ohm083062a(n) has a variable

30、 resistance. volume control is an example that makes use of it.rheostat083063the resistance of the wire depends on what it is made of. it also depends on its and its .length, thickness083064every fuse has a number printed on it. if the current exceeds this number, the fuse out. the number is called

31、the fuse .blows/is blown, rating083065ethe power of an electrical appliance is measured in , written in symbol .watt, w083066ewe use a meter to measure the amount of electrical energy used. kilowatt-hour083067eelectrical energy consumed by an electrical appliance can be measured in (symbol ) or in (

32、symbol ) in household sector.joule/kilojoule, j/kj, kilowatt-hour, kw h083068epower of an electrical appliance = ( passing through it) ( applied to it)current, voltage083069ea(n) is made up of a current-carrying coil. it attracts things that made of .electromagnet, iron083070eboth electric bells and

33、 loud speakers make use of the effect of current.magnetic d short questions084071draw a circuit diagram of the following setup.- ans - ans end -084072draw lines to join the bulbs in series and in parallel.a series circuita parallel circuit- ans -a series circuita parallel circuit- ans end -084073fin

34、d out the position of the sliding contact of the rheostat at which the bulb will be the brightest. give a reason for your answer.cbawhen the contact is at position c, the bulb gives the max. brightness because the length of the wire is the shortest at c for electric current to flow. so, the resistan

35、ce is the smallest. as a result, the electric current is the greatest.084074explain why the light bulb in the following circuit can never light up?it is because the light bulb is short-circuited. current bypasses the bulb by taking the branch in the middle.084075write three things that should not be

36、 done if we want to use electricity safely, e.g. remove the plug from a socket by pulling the cable.overload a socket.switch appliances on and off with wet hands.replace fuse until the fault has been traced and put right.plug in an electrical appliance when the switch is on.(any three)084076write th

37、ree things that should be done if we want to use electricity safely, e.g. replace damaged cables, sockets and plugs immediately.use three-pin plugs with proper earthing.use the fuse with the correct fuse rating.keep cables away from water.turn off the electrical appliance before removing its plug fr

38、om the socket.(any three)084077eif 1 kw h costs $1, calculate how long has a 200 w lamp been used, if $10 is spent for it. (show your steps.)no. of kw h used = 10 / 1 = 10time = 10 kw h / 0.2 kw = 50 hours(note 200 w = 0.2 kw)084078ewhat happens to the iron nails when the circuit is closed? why?the

39、iron nails will be attracted to the coil because the coil turns into an electromagnet when current passes through it.084079calculate the current flowing through point d. what happens if point d is broken?ebcad0.3 a3 vn ans n let x a be the current flowing in branch cen so, x + 2x = 0.3n x = 0.1curre

40、nt flowing through point d is 0.1 athe bulbs in ce go out. the bulb in ab remains unaffected.- ans end -084080if the voltmeter reads 1 v and the ammeter reads 0.1 a, what is the amount of energy used by the bulb in 1 hour? express your answer in joule.0.1 a1 v- ans -power of the bulb = 1 v 0.1 a = 0

41、.1 w amount of energy used in 1 hour = 0.1 3600 s = 360 j- ans end -084114ewhat is the device that is formed from current flowing through a coil?electromagnet084115what does this circuit symbol represent? bulbe long questions085081the following table shows the result of an experiment testing the abi

42、lity of different substances to conduct electricity. the length and thickness of the sample wires are equal. the voltage applied is the same in each trial.substancecurrentcopper0.1 aglass0 agold0.13 anickel0.02 awood0 aagiven some non-conducting substance x. according to the above result, is it more

43、 likely to be a metal or non-metal?bshould we connect the ammeter to the sample in series or in parallel?cconsider the copper, gold and nickel wire. arrange these three wires in the ascending order of their resistance.dwhich of the above three substances has the greatest heating effect when an equal

44、 amount of current passes through it?einterestingly, the copper wire is a very good conductor but it gets very hot in a short circuit. why?anon-metal. the result suggests that metals are conductors, while these non-metals are insulators.bin seriescgold, copper, nickeldnickelebecause the current is v

45、ery large and this makes the heating effect strong.085082study the following circuit carefully and answer the following questions.ybcaxaif the switch a is closed, but b and c are open, which bulb will light up?bif the switch c is closed, but a and b are open, which bulb will light up?cif the switche

46、s a and c are closed, but b is open, which bulb will light up?dwhat is the type of the circuit in (c) called?eif the switch b is closed, a and c is open, which bulb will light up?fwhat is the type of the circuit in (e)?gif the switches a, b and c are all closed, which bulb will light up?abulb xbbulb

47、 ycbulbs x and ydparallel circuitebulbs x and yfseries circuitgnone085083all the light bulbs in the following circuit are identical.0.1 a0.2 aabawhich bulb is the brightest when the circuit is closed?bdraw in the above diagram to show how to measure the voltage of bulb b.ccalculate the total amount

48、of current being drawn from the battery.dif bulb b burns out, what happens to bulb?ewhat rating (0.5 a, 1 a or 2 a) should be used if a fuse is added to the circuit to protect the bulbs as in the diagram?- ans -abulb abc0.2 a + 0.1 a = 0.3 adbulb a remains unaffected.e0.5 a- ans end -085084the follo

49、wing diagram shows two circuits, p and q. the light bulbs in both circuits are identical.circuit pcircuit qawhich circuit is a parallel circuit, which one is a series circuit?bthe bulbs in which circuit would be dimmer? why?cif the cell supplies a voltage of 1.5 v, what is the voltage applied to the

50、 outermost bulb in circuit p?dif one bulb in circuit q burns out , will the other two still operate?ewhich kind of circuit, p or q, is usually found in the house? why?acircuit p is a parallel circuit. circuit q is a series circuit.bthe bulbs in circuit q is dimmer because the voltage across each bulb is lower.c1.5 v.dbulbs d and f will go out.ecircuit p. in such circuits, electrical appliances work independently, unaffected by each other.