## Sunday, March 15, 2015

### Revision Questions for AISSE Physics for SA 1

ELECTRICITY
1. Define electric potential difference?
2. Why is an ammeter connected in series in a circuit?
3. Why is a voltmeter connected in parallel in a circuit?
4. State the law that governs the strength of the current passing through a metallic conductor when a p.d is applied across its end. Illustrate this law graphically?
5. State the law which governs the amount of heat produced in a metallic conductor when current is passed through it for a given time. Express this law mathematically?
6. Define resistance. What are the factors on which it depends?
7. A copper wire of resitivity P is stretched to reduce its diameter to half its previous value. What is the new resistivity?
8. Define the S I unit of electric current and potential difference.
9. Derive expressions for equivalent resistance of resistors connected in a. series combination b. parallel.  combination
10. What is an electric fuse? Explain its function.
11. Explain, how the heating effect of electric current is made use in the functioning of an electric bulb?
12. State the relation between the commercial and SI unit of electric energy.
13. Write the advantages of connecting electrical appliances in parallel and disadvantages of connecting them in series in a household circuit.
14. Why is tungsten used almost exclusively for making the filaments of electric lamps?
15.  A piece of wire is redrawn by pulling it until its length is doubled .Compare the new resistance with the original value.
16. An electric geyser has rating 2000 w, 220 v marked on it. What should be the minimum rating in whole number of a fuse wire that may be required for safe use with the geyser?
17.  Three resistors each of resistance 10 ohm are connected, in turn, to obtain a. minimum resistance b. Maximum resistance. Compute a)  The effective resistance in each case b) The ratio of minimum to maximum resistance so obtained.
18. Two resistors of resistance 2 ohms and 4 ohms are, in turn connected a)  In series b)  In parallel to a given battery for same interval. Compute the ratio of the total quantity of heat produced in the  combination in the two cases.
19.  Two metallic wires A and B are connected in parallel. Wire A has length L and radius R wire B has a length 2L and radius 2r. Compute the ratio of the total resistance of parallel combination and resistance of wire A.
20. In a house three bulb of 100w each are lighted for 4 hours daily and six tube lights of 20w each are lighted for 5 hours daily and a refrigerator of 400w is worked for 10 hours daily for a month of 30 days. Calculate the electricity bill if the cost of one unit is Rs 4.00.
21. Three resistors of 4ohms, 6ohms and 12 ohms are connected in parallel. The combination of above resistors is connected in series to a resistance of 2 ohms and then to a battery of 6 volts. Draw a circuit diagram and calculate a) Current in main circuit b) Current flowing through each of the resistors in parallel c) P.d and the power used by the 2 ohm resistor.
22.  Two lamps, one rated 100 W at 220 V and the other 60W at 220 V, are connected in Parallel to a 220 volt supply. What current is drawn from the supply line?
Magnetic Effects of Current
1. What is a magnetic field? What are field lines around a magnet?
2.  List the characteristic properties of magnetic field lines.
3.  Sketch the pattern of magnetic field lines around a bar magnet.
4.  Sketch the pattern of magnetic field lines around a current-carrying straight conductor and state the factors on which the strength of magnetic field depends.
5. State right hand thumb rule to find the direction of magnetic field around a current â€“carrying straight conductor. How will this magnetic field be affected on (a) Increasing the current through the conductor. (b) Changing the direction of flow of current in the conductor.
6. A student performs an experiment to study the magnetic effect of current around a current-carrying straight conductor. He reports that (a) The direction of deflection of thenorth pole of the compass needle kept at a given point near the conductor remains unaffected even when the terminals of the battery sending current in the wire are interchanged. (b) For a give battery, the degree of deflection of N pole decreases when the compass is kept at a farther away from the conductor. Which of the above observations of the student is incorrect and why?
7.  Describe with a neat diagram an activity to show that a straight conductor carrying direct current produces a magnetic field around it. State the rule which determines the direction of magnetic field thus produced.
8. Draw the lines of force (indicating the direction) of magnetic field through and around (a) a single loop of wire carrying direct current. (b) a solenoid carrying direct current.
9. What are the factors on which the magnetic field due to a current-carrying circular coil depends? Also explain the pattern of field lines produced in and around a circular coil.
10.  Draw the pattern of magnetic field lines of a current-carrying solenoid. What does the pattern of field lines inside a solenoid indicate? Write one application of magnetic field of current-carrying solenoid.
11.  What is an electro-magnet? Draw a diagram showing an electro-magnet.
12.  The magnetic field in a given region is uniform. Draw a diagram to represent it.
13.  (a) Describe with diagram an experiment to show that a force is exerted on a current-carrying conductor when placed perpendicular in amagnetic field. (b) State the rule to find the direction of the force exerted on a current-carrying conductor in a magnetic field . (c) A current-carrying straight conductor is placed in the East-West direction. What will the direction experienced by the conductor due to earthâ€™smagnetic field?
14.  Why does a current-carrying conductor kept in a magnetic field experience force? On what factors does the direction of this force depend? Name and state the rule used for determination of direction of this force.
15.  With a labeled diagram, describe the construction and working of an electric motor. What is the function of split ring commutator in a motor?
16.  What is the use of a commutator? Name the component in an electric motor which acts as a commutator.
17. What is an armature? Mention the alternative methods adopted in commercial motors to enhance their power.
18. . Explain the principle of an electric motor. Name some appliances in which the electric motor is used.
19. A positively charged particle projected towards West is deflected towards North by a magnetic field. What is the direction of the magnetic field?
20. . Explain the meaning of the word â€œelectro-magneticâ€ and â€œinductionâ€ in the term electro-magnetic induction. On what factors does the value of induced current produced in a circuit depend? Name and state the rule used for determination of direction of induced current. State one practical application of this phenomenon in everyday life.
21. . Why is electro-magnetic induction so called? A coil connected to a sensitive galvanometer is held stationary. A bar magnet with its North Pole facing coil is moving towards the coil at a certain speed. The galvano meter needle shows deflection of 10 divisions to towards right of the centre of the scale. How will the reading on the galvanometer scale be affected if the south pole of the bar magnet facing the coil is moved away at the same speed?
22.  Describe an activity to demonstrate the phenomenon of electro-magnetic induction.
23.  State Flemingâ€™s right hand rule. How is this rule useful?
24. Explain different ways to induce current in a coil.
25. (a) With the help of a neat labeled diagram, explain the construction and working of an electric generator. What is the function of bushes? (b) How does a D.C generator differ from that of A.C generator?
26.  How does A.C differ from D.C? Which sources produce alternating current? What is the frequency of alternating current in India
27.  Draw a schematic labeled diagram of a domestic electric circuit which includes a mains fuse, a power meter, a light point, a fan and a power plug.
28.  What do you mean by (a) short circuit and (b) overloading? What are the safety precautions taken to avoid these problems in domestic electric circuits?
29. (a) An electrician put a fuse rating of 5A in that part of domestic electric circuit in which an electric heater of rating 1.5kW, 220V is operating. What is likely to happen in this and why? What change, if any, needs to be made? (b) You are given the following current time graphs from two different sources. (i) Name the type of current in two cases. (ii) Identify any one source for each type of these currents. (iii) What is the frequency of current in case II in India? (iv)Use above graphs to write two differences between the current in two cases.
30.  An electrician assembling a household circuit uses a long thick copper wire with green insulation and a short wire made up of copper-tin alloy. What are the two wires called? Mention the importance of each wire in an electric circuit. How are the two wires connected in the circuit?