UNIQUE SCIENCE ACADEMY

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1 1 UIQUE IEE EMY Test (Unit 21) ame :... Paper: Physics ate :... ode: 5054 lass: II Time llowed: 40Minutes This document consists of 6 printed pages. Maximum Marks: 25 T [Total 15 Marks] heory ection: Fig. 1.1 shows a metal bar placed inside a vertical solenoid. 1 metal bar d.c. power supply + solenoid iron paper-clips Fig.1.1 The solenoid is a coil of several turns of insulated wire. d.c. power supply is connected to the solenoid so that there is a current in it when the supply is switched on. The metal bar is a short distance above a small pile of iron paper-clips in a glass dish. The power supply is switched on, left on for several seconds, then switched off. escribe the behaviour of the paper-clips when this procedure is carried out using a metal bar of (a) aluminium,... (b) iron,...[2] (c) steel....[2] [Total 5] edicated to My on Mohammad Irtaza Zain. ode 5054 [Turn over

2 2 The circuit in Fig. 2.1 shows an electromagnetic relay being used to switch an electric motor on and off. The relay coil has a much greater resistance than the potential divider. 6 V pivoted iron armature 2 power supply for motor switch M motor relay core Fig. 2.1 contacts (a) The relay operates when there is a potential difference of 3 V across the coil. On Fig. 2.1, mark the position of the slider of the potential divider when the relay just operates. (b) escribe how the relay closes the contacts in the motor circuit [3] [Total: 4] (a) n iron rod is placed next to a bar magnet, as shown in Fig (i) (ii) iron rod Fig. 3.1 On Fig. 3.1, mark clearly the north pole and the south pole that are induced in the iron rod. What happens to the magnet and the rod? Tick one box. second bar magnet is now placed next to the iron rod, as shown in Fig iron rod Fig. 3.2 On Fig. 3.2, mark clearly the magnetic poles induced in the iron rod. What happens to the iron rod and the second magnet? Tick one box. edicated to My on Mohammad Irtaza Zain. ode 5054 [Turn over

3 (c) The iron rod is removed, leaving the two magnets, as shown in Fig Fig. 3.3 What happens to the two magnets? Tick one box. 3 (d) The second magnet is removed and replaced by a charged plastic rod, as shown in Fig Fig. 3.4 charged plastic rod What happens to the magnet and the plastic rod? Tick one box. 1 MQ ETIO:[Total 10 Marks] [Total: 6] brass rod is positioned in an east-west direction and a plotting compass is placed at each end. brass rod plotting compass Which diagram shows the positions of the needles of the plotting compasses? 5 2 solenoid carrying a current is used to demagnetise a bar magnet. solenoid bar magnet power supply Which conditions achieve demagnetisation? current through solenoid movement of bar magnet a.c. around the solenoid quickly a.c. through the solenoid slowly d.c. around the solenoid quickly d.c. through the solenoid slowly edicated to My on Mohammad Irtaza Zain. ode 5054 [Turn over

4 4 3 The north pole of a bar magnet is placed next to end P of an iron bar PQ, as shown. s a result, magnetic poles are induced in the iron bar. P Q magnet What are the magnetic poles induced at P and at Q? iron bar magnetic pole at P magnetic pole at Q north north north south south north south south 4 5 n electromagnet is used to separate magnetic metals from non-magnetic metals. Why is steel unsuitable as the core of the electromagnet? It forms a permanent magnet. It has a high density. It has a high thermal capacity. It is a good conductor of electricity. chain of steel nails and a chain of iron nails hang from a strong magnet. The chains are then carefully removed from the magnet. magnet steel iron What happens to the chains? oth chains fall apart. Only the chain of iron nails falls apart. oth chains stay together. Only the chain of steel nails falls apart. 6 Which statement about a magnet is not correct? It can attract another magnet. It can attract an unmagnetised piece of iron. It can repel another magnet. It can repel an unmagnetised piece of iron. edicated to My on Mohammad Irtaza Zain. ode 5054 [Turn over

5 5 7 The diagram shows an alarm system in which the switch is shown closed. pivot iron core iron metal bell What happens when the switch is opened? iron bell drops rings drops stops ringing moves up rings moves up stops ringing 8 permanent magnet can be demagnetised by using a solenoid and switching the current on then off. Which diagram shows the most effective method of producing demagnetisation? magnet left in place magnet withdrawn before switching off magnet left in place magnet withdrawn before switching off edicated to My on Mohammad Irtaza Zain. ode 5054 [Turn over

6 9 Four metal rods are placed, in turn, inside a coil of copper wire. current in coil 6 metal rod paper clips Each rod is used to pick up as many paper clips as possible. The current is then switched off. The table gives the results of the experiment. Which rod is the most suitable core for a coil in a circuit breaker? number of paper clips picked up when there is a current in the coil number of paper clips still attached after the current is switched off n iron nail can be magnetised using a coil. How can the nail be demagnetised? leaving the apparatus switched on for a long time removing the nail from the coil while using an a.c. supply using a coil with fewer turns using more cells MQ nswer heet edicated to My on Mohammad Irtaza Zain. ode 5054