UPSC General Science : Electro Magnetic Notes Part 1

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Today’s Topic: Electro Magnetic

Q1. Which of the following statements is/are correct:

1) Producer gas is a mixture of CO and N2.

2) Water gas burn with a smoke less flame.

3) Producer gas used in manufacture of coal gas and to operate gas engines.

Choose correct options

a) 1 and 2

b) 2 and 3

c) All of the above

d) None of these.

Ans:     C

Explanation:    Producer gas is made by air passing over red hot coke. As a result, some of the coke burns to CO2 at the bottom of the furnace. This gas reduced to carbon monoxide (CO) as it passes through the upper layer of red hot coke. Formation of producer gas is exothermic reaction. Water gas is a mixture of carbon monoxide and hydrogen (CO=H2) is prepared when steam is passed over red hot coke.

Q2. Match the following List-1 and List-2:

1) Philospher wool

2) Green vitriol

3) Marble

4) Blue vitriol Chemical Formulae:

a) ZnO

b) CACO3

c) FeSO4, 7H2O

d) CuSO4, 5H2O


A         B          C          D

a) 1         3          2          4

b) 4         2          1          3

c) 2         4          1          3

d) 1         2          3          4

Ans:     A


Philospher wool          –           ZnO

Marble                         –           CaCo3

Green vitriol                –           FeSO4, 7H2O

Blue vitriol                   –           CuSO4, 5H2O

Q3. Magnets is effected by:

a) Heating

b) Magnetising in the opposite direction

c) Rough handling

d) All of the above.

Ans:     D

Explanation:    If a coil wrapped on a magnet and an alternating current is passed through the coil, the magnet is demagnetised. It can be demagnetised by holding it in E-W direction. The rough handling of a magnet also demagnetised it. If a magnet heated and then hammered its magnetism is destroyed. If two similar magnet are placed in such a way that their likes pole are near each other and they becomes weak strength.

Q4. Diamagnetic substances differ from the para-magnetic and ferromagnetic substance in which one of the following ways:

a) They settle with long axis normal to the magnetic field.

b) Diamagnetic substances are repelled by magnet.

c) Diamagnetic substances are feebly attracted by a magnet.

d) Both (a) and (c).

Ans:     D

Explanation:    Diamagnetic substances tend to move from stronger to weaker parts of the magnetic field. Diamagnetic substances are bismuth, copper, mercury, antimony gold, water, alcohol, air and hydrogen. When a diamagnetic material is suspended sets itself at right angle to the direction of the field. The concentration of magnetic lines of force is more outside the specimen.

Q5. Which one of the following is essential differences between AC dynamo and DC dynamo:

a) AC dynamo has a coil wound on soft iron but the coil in DC dynamo is wound on copper.

b) AC dynamo will generate a higher voltage.

c) AC dynamo has shp ring but DC dynamo has a commutator.

d) None of the above.

Ans:     C

Explanation:    The DC dynamo has a commutator or current reverie. In AC dynamo the end of Armature coil are connected then insulated ship ring which are mounted on the armature shaft. So in above option(c) is essential difference between AC and DC dynamo.

Q6. Which one of the following is correct about Canada balsam:

a) It is type of jet engine.

B) It is adevice to store electric charge.

C) It is a protein deficiency syndrome.

D) It is a transparent adhnesive for glass.

Ans:     D

Explanation:    Cannada Balsam is a transparent adhnesive for glass. Having the same refractive index as glass. It is used for cementing together precision optional element so option (d) is correct about Canada balsam.

Q7. There are streaks of colour on a car windshield shortly after it has been swiped by a windshield wiper or a at a gas station. It result from which one of the following.

a) Dispersion of light

b) Scattering of light

c) Absorption of heat

d) Interferences of light

Ans:     D

Explanation:    These streaks of colour are the result of interferences of light by the very thin film of oil that is spread over the water surface. This from the interference is commonly called thin film interference. When light wave from two independent, near by a coherent sources or LASER beam is interact with each other. They may either destroy or strengthen each other giving rise to alternate dark and light band.

Q8. Which one of the following required for converting Ammeter into Voltmeter:

a) A low resistance either in series or parallel

b) High resistance in series and removal of shunt

c) Low resistance in parallel

d) Low resistance in series

Ans:     B

Explanation:    A voltmeter is always connected across that part of circuit where potential difference is to be measure. In order that the insertion of a voltmeter in the circuit does not change the current. The voltmeter must have high resistance since the coil of the instrument does not have a large resistance of its own. To convert an Ammeter into voltmeter high resistance is series and removal of shunt required.

Q9. On which one of the following hydrogen bomb is based:

a) Controlled fusion

b) Uncontrolled fusion

c) Controlled fission

d) Uncontrolled fission

Ans:     B

Explanation:    In the hydrogen bomb fusion of light nucleus take place and tremendous amount of energy released. In this part bomb fission-fusion process is applied. The central part contains a fission bomb containing uranium – 235 or plutonium – 239.

Q10. Specific resistance of a wire depends upon which of the following:

a) Mass

b) Cross section

c) Length

d) Nature of the material of wire

Ans      D

Explanation:    The specific resistance of a wire do not depend upon mass, cross section and length of wire. It will depend only on the nature of the material of the wire so option (d) is correct answer.