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Sample 1 Mark Book Back Questions (New Syllabus) 2020

12th Standard EM

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Physics

Time : 00:20:00 Hrs
Total Marks : 20

    Part A

    20 x 1 = 20
  1. Two points A and B are maintained at a potential of 7 V and -4 V respectively. The work done in moving 50 electrons from A to B is

    (a)

    8.80 × 10-17 J

    (b)

    -8.80 × 10-17 J

    (c)

    4.40 × 10-17 J

    (d)

    5.80 × 10-17 J

  2. A parallel plate capacitor stores a charge Q at a voltage V. Suppose the area of the parallel plate capacitor and the distance between the plates are each doubled then which is the quantity that will change?

    (a)

    Capacitance

    (b)

    Charge

    (c)

    Voltage

    (d)

    Energy density

  3. The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 Ω is

    (a)

    0.2 Ω

    (b)

    0.5 Ω

    (c)

    0.8 Ω

    (d)

    1.0 Ω

  4. A thin insulated wire forms a plane spiral of N = 100 tight turns carrying a current I = 8 m A (milli ampere). The radii of inside and outside turns are a = 50 mm and b = 100 mm respectively.
    The magnetic induction at the center of the spiral is

    (a)

    \(5\mu T\)

    (b)

    \(7\mu T\)

    (c)

    \(8\mu T\)

    (d)

    \(10\mu T\)

  5. A non-conducting charged ring of charge q, mass m and radius r is rotated with constant angular speed ω. Find the ratio of its magnetic moment with angular momentum is

    (a)

    \(\\ \frac { q }{ m } \)

    (b)

    \(\\ \frac { 2q }{ m } \)

    (c)

    \(\\ \frac { q }{ 2m } \)

    (d)

    \(\\ \frac { q }{ 4m } \)

  6. Th e fl ux linked with a coil at any instant t is given by \(\Phi\)B =10t2−50t+ 250 . The induced emf at t = 3s is

    (a)

    −190 V

    (b)

    −10 V

    (c)

    10 V

    (d)

    190 V

  7. A circular coil with a cross-sectional area of 4 cm2 has 10 turns. It is placed at the centre of a long solenoid that has 15 turns/cm and a cross-sectional area of 10 cm2. The axis of the coil coincides with the axis of the solenoid. What is their mutual inductance?

    (a)

    7.54 μH

    (b)

    8.54 μH

    (c)

    9.54 μH

    (d)

    10.54 μH

  8. Which of the following are false for electromagnetic waves

    (a)

    transverse

    (b)

    mechanical waves

    (c)

    longitudinal

    (d)

    produced by accelerating charges

  9. A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that its end closer to the pole is 20 cm away from the mirror. The length of the image is,

    (a)

    2.5 cm

    (b)

    5cm

    (c)

    10 cm

    (d)

    15cm

  10. In a Young’s double-slit experiment, the slit separation is doubled. To maintain the same fringe spacing on the screen, the screen-to-slit distance D must be changed to,

    (a)

    2D

    (b)

    \(\frac{D}{2}\)

    (c)

    \(\sqrt{2}\)D

    (d)

    \(\frac{D}{\sqrt2}\)

  11. Light transmitted by Nicol prism is,

    (a)

    partially polarised

    (b)

    unpolarised

    (c)

    plane polarised

    (d)

    elliptically polarised

  12. If a light of wavelength 330 nm is incident on a metal with work function 3.55 eV, the electrons are emitted. Then the wavelength of the emitted electron is (Take h = 6.6 × 10–34 Js)

    (a)

    <2.75×10−9m

    (b)

    ≥2.75×10−9m

    (c)

    ≤2.75×10−12m

    (d)

    <2.5×10−10m

  13. Photons of wavelength λ are incident on a metal. The most energetic electrons ejected from the metal are bent into a circular arc of radius R by a perpendicular magnetic field having magnitude B. The work function of the metal is

    (a)

    \(\frac { hc }{ \lambda } -{ m }_{ e }+\frac { e^{ 2 }{ B }^{ 2 }{ R }^{ 2 } }{ { 2m }_{ e } } \)

    (b)

    \(\frac { hc }{ \lambda } +{ 2m }_{ e }{ \left[ \frac { eBR }{ { 2m }_{ e } } \right] }^{ 2 }\)

    (c)

    \(\\ \frac { hc }{ \lambda } -{ m }_{ e }{ c }^{ 2 }-\frac { e^{ 2 }{ B }^{ 2 }{ R }^{ 2 } }{ { 2m }_{ e } } \)

    (d)

    \(\frac { hc }{ \lambda } -{ 2m }_{ e }{ \left[ \frac { eBR }{ { 2m }_{ e } } \right] }^{ 2 }\)

  14. The charge of cathode rays is

    (a)

    Positive

    (b)

    negative

    (c)

    neutral

    (d)

    not defined

  15. A radioactive nucleus (initial mass number A and atomic number Z) emits 2α and 2 positrons. The ratio of number of neutrons to that of proton in the final nucleus will be

    (a)

    \(\frac{A-Z-4}{Z-2}\)

    (b)

    \(\frac{A-Z-2}{Z-6}\)

    (c)

    \(\frac{A-Z-4}{Z-6}\)

    (d)

    \(\frac{A-Z-12}{Z-4}\)

  16. If a half –wave rectifi ed voltage is fed to a load resistor, which part of a cycle the load current will flow?

    (a)

    00–900

    (b)

    900–1800

    (c)

    00–1800

    (d)

    00–3600

  17. When a transistor is fully switched on, it is said to be

    (a)

    Shorted

    (b)

    Saturated

    (c)

    Cut-off

    (d)

    Open

  18. The variation of frequency of carrier wave with respect to the amplitude of the modulating signal is called _______.

    (a)

    Amplitude modulation

    (b)

    Frequency modulation

    (c)

    Phase modulation

    (d)

    Pulse width modulation

  19. The materials used in Robotics are

    (a)

    Aluminium and silver

    (b)

    Silver and gold

    (c)

    Copper and gold

    (d)

    Steel and aluminum

  20. The gravitational waves were theoretically proposed by

    (a)

    Conrad Rontgen

    (b)

    Marie Curie

    (c)

    Albert Einstein

    (d)

    Edward Purcell

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