Class XII Physics Paper Held on 02 March 2020
Unofficial Answer Key
Set: 1 Code: 55/2/1 Series: HMJ/2
Section: A
NOTE: MULTIPLE CHOICE QUESTIONS
Q1. A cell of internal resistance r connected across an external resistances R can supply maximum current when
Answer: (a) R=r
Q2. In a current carrying conductor the ratio of the electric field and the current density at a point is called:
Answer: (a) Resistivity
Q3. An electron is released from rest in a region of uniform electric and magnetic fields acting to each other. The electron will
Answer: (a) move in the straight line
Q4. Above Curie temperature, a
Answer: (b) ferromagnetic material becomes paramagnetic.
Q5. Displacement current exist only when
Answer: (a) Electric field is changing
Q6. Electromagnetic wave is used as diagnostic tool in medicine are
Answer: (a) X - rays.
Q7. AT equilibrium, in a p-n junction diode the net current is
Answer: (c) zero as diffusion and drift currents are equal and opposite.
Q8. In an n-type semiconductor, the donor energy level lies
Answer: (b) just below the conduction band
Q9. When two nuclei (A≤ 10) fused together to form a heavier nucleus, the
Answer: (a) binding energy per nucleon increases.
Q10. In β- decay, a
Answer: (a) neutron converts into a proton emitting antineutrino.
FILL IN THE BLANKS WITH APPROPRIATE ANSWER:
Q11. If the electric flux entering and leaving a closed surface in air are φ1 and φ2 respectively, the net electric charge enclosed within the surface is___________ :
Answer: (φ2 - φ1) x ϵo.
Q12. In young's double slit experiment the
path difference between two interfering waves at a point on the screen is 5l/2 , l being
wavelength of light used. The __________ dark fringe will lie at this point.
Answer: Third
OR
If one of the slit in Young’s double slit experiment
is fully closed, the new pattern has ___________ central maximum in angular
size.
Answer: bright
Q13. For a higher resolving power of a compound
microscope, the wavelength of light used should be ___________.
Answer: Minimum/least.
Q14. Unpolarised light passes from a rear into a
denser medium. If the reflected and the refracted rays are mutually
perpendicular, the reflected light is linearly polarised _________ to the plane
of incidence.
Answer: Perpendicular
Q15. Out of red, blue and yellow lights, the
scattering of_____ light is maximum.
Answer: Blue
NOTE: ANSWER THE FOLLOWING
Q16. What is the impedance of a capacitor of capacitance C in an ac circuit using source of frequency n Hz?
Answer:
OR
What is the value of impedance of a resonant series LCR circuit?
Answer:
Q17. A conducting rod of length l is kept parallel to a uniform magnetic field vector B. It is moved along the magnetic field with a velocity vector v. What is the value of emf induced in the conductor?
Answer:
Q18. Draw the graph showing variation of the value of the induced emf as a function of rate of change of current flowing through an ideal inductor.
Answer:
Q19. What is the wavelength of a photon of energy 3.3 x 10 – 19 J?
Answer:
Q20. Define the term "threshold frequency" in photoelectric emission.
Answer: Threshold frequency is defined as the minimum frequency of incident light which can cause photo electric emission i.e. this frequency is just able to eject electrons with out giving them additional energy.
NOTE: SECTION B, SECTION C and SECTION D will be uploaded soon.
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