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12th Standard Physics Current Electricity English Medium Free Online Test One Mark questions with Answer Key 2020 - 2021

12th Standard EM

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Physics

Time : 00:20:00 Hrs
Total Marks : 20
    Answer all the questions
    20 x 1 = 20
  1. A wire of resistance 2 ohms per meter is bent to form a circle of radius 1m. Th e equivalent resistance between its two diametrically opposite points, A and B as shown in the fi gure is

    (a)

    \(\pi \Omega\)

    (b)

    \(\frac{\pi}{2}\Omega\)

    (c)

    2\(\pi \Omega\)​​​​​​​

    (d)

    \(\frac{\pi}{4}\Omega\)

  2. A carbon resistor of (47 ± 4.7 ) k Ω to be marked with rings of diff erent colours for its identifi cation. Th e colour code sequence will be

    (a)

    Yellow – Green – Violet – Gold

    (b)

    Yellow – Violet – Orange – Silver

    (c)

    Violet – Yellow – Orange – Silver

    (d)

    Green – Orange – Violet - Gold

  3. There is a current of 1.0 A in the circuit shown below. What is the resistance of P ?

    (a)

    1.5 Ω

    (b)

    2.5 Ω

    (c)

    3.5 Ω

    (d)

    4.5 Ω

  4. The temperature coefficient of resistance of a wire is 0.00125 per °C. At 300 K, its resistance is 1 Ω. The resistance of the wire will be 2 Ω at

    (a)

    1154 K

    (b)

    1100 K

    (c)

    1400 K

    (d)

    1127 K

  5. The electrical resistivity of a thin copper wire and a thick copper wire are respectively \({ P }_{ 1 }\Omega \) m and \({ P }_{ 2 }\Omega \) m Then.

    (a)

    \({ P }_{ 1 }>{ P }_{ 2 }\)

    (b)

    \({ P }_{ 2 }>{ P }_{ 1 }\)

    (c)

    \({ P }_{ 1 }={ P }_{ 2 }\)

    (d)

    \(\cfrac { { P }_{ 1 } }{ { P }_{ 2 } } \)

  6. Which of the following has negative temperature coefficient of resistance?

    (a)

    copper

    (b)

    tungsten

    (c)

    carbon

    (d)

    silver

  7. The potential difference across the terminals of a cell varies with the current drown from
    the cell according to the graph.

    (a)

    (b)

    (c)

    (d)

  8. Resistance between the points A and B in the given figure is

    (a)

    \(9\Omega \)

    (b)

    \(2\Omega \quad \)

    (c)

    \(3\Omega \)

    (d)

    \(6\Omega \)

  9. Nichrome wire is used as the heating element because it has

    (a)

    low specific resistance

    (b)

    low melting point

    (c)

    high specific resistance

    (d)

    high specific resistance

  10. Fuse wire is an alloy of

    (a)

    37 % lead and 63 % tin

    (b)

    63 % lead and 37 % tin

    (c)

    37 % copper and 63 % tin

    (d)

    63 % copper and 37 % tin

  11. The ratio of voltage and current in a dosed circuit

    (a)

    decreases

    (b)

    increases

    (c)

    remains constant

    (d)

    varies

  12. By increasing the temperature, the specific resistance of a conductor and a semiconductor

    (a)

    increases for both

    (b)

    increases, decreases respectively

    (c)

    decreases for both

    (d)

    decreases, increases respectively

  13. Which energy is used to liberate the outer electron from the individual atoms?

    (a)

    Thermostatic external energy

    (b)

    Thermodynamic internal energy

    (c)

    Thermodynamic external energy

    (d)

    Thermostatic internal energy

  14. Melting point of a tungsten filament inside a glass bulb is_________

    (a)

    3360o C

    (b)

    3340oC

    (c)

    3380oC

    (d)

    3370oC

  15. Kirchoff's II law isa consequence of conservation of________

    (a)

    eharges

    (b)

    momentum

    (c)

    energy

    (d)

    power

  16. A potential of 1 kV is applied between the ends of conductor of length 20 cm. The drift velocity of electron in this field is 3.52 x 106 m/s. The relaxation time for the freeelectrons is

    (a)

    2 nano sec

    (b)

    4 nano sec.

    (c)

    6 nano sec

    (d)

    8 nano sec.

  17. The specific resistance for the insulators is in the range of________

    (a)

    10-610-8\(\Omega m\)

    (b)

    108-1014\(\Omega m\)

    (c)

    10-8-10-14\(\Omega m\)

    (d)

    10-8-1014\(\Omega m\)

  18. Super conductors can be used as storage elements in_________

    (a)

    TV

    (b)

    camera

    (c)

    computers

    (d)

    computers

  19. The temperature coefficient of resistance increases for the metals when________

    (a)

    the temperature increases

    (b)

    the temperature decreases

    (c)

    does not depend upon the temp~rature

    (d)

    either (a) or (b)

  20. Kirchhoff's I law is named as_____________

    (a)

    ohm's law

    (b)

    voltage law

    (c)

    resistance law

    (d)

    current law

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