CBSE 12th Board 2014 Physics exam has been completed. Most of the candidates are in situation regarding their Physics papers that may disturb their CBSE 12th marks and percentage. CBSE too believe that Physics paper was lengthy and tricky but not tough.
Approx 11 Lakhs candidates appeared in Physics paper that was on 5th March 2014. CBSE also schedule the paper in starting to test more knowledge and skills of candidates. However most of the students are in bitter situation after the paper. Paper was tricky and lengthy but well preparation plan and strategy could also break the paper to crack marks around 60-65.
We are providing solutions of some tricky questions only rest answers can easily be searched in NCERT books. All derivations were asked from NCERT Books whose solutions are available in the books. Candidates can easily check their solutions in NCERT books that is always recommended by CBSE for any exams.
CBSE 12th Physics Questions 2014 with Solutions for all Sets
1. Define the term ‘Mobility’ of charge carriers in a conductor. Write its S.I. unit
Solution: Mobility of charge carriers in a conductor is defined as the magnitude of their drift velocity per unit applied electric field.
Mobility, μ=Drift velocity Electric field
We know μ=VdE
2. “For any charge configuration, equipotential surface through a point is normal to the electric field.” Justify.
Solution: We know that the work done (W) in moving a test charge along an equipotential surface is zero. This is because an equipotential surface is a surface with a constant values of potentialat all the points on the surface.
∴ W = Fs cosθ = 0, θ = 90°
Here, F is the electric force and s is the magnitude of displacement of the charge. For non-zero displacement, this is possible only when cosθ is equal to 0. i.e. cosθ = 0
3. Two spherical bobs, one metallic and the other of glass, of the same size are allowed to fall freely from the same height above the ground. Which of the two would reach earlier and why?
Solution: A glass bob is non-conducting, while a metallic bob is conducting. Due to the non-conducting nature of the glass bob, it will only experience the Earth’s gravitational pull. So, the glass bob will reach the ground earlier.
Because of its conducting nature, Eddy current is induced in the metallic bob as it falls through the magnetic field of the Earth.
By Lenz’s law, the current induced is such that it opposes the motion of the metallic bob. So, the metallic bob will experience a force in the upward direction. This will slow down the metallic bob by some extent. Hence, it will reach the Earth after the glass bob.
4. Write the expression, in a vector form, for the Lorentz magnetic force F→ due to a charge moving with velocity V→ in a magnetic field B→. What is the direction of the magnetic force?
Solution: The Lorentz magnetic force is given by the following relation:
Here, q is the magnitude of the moving charge.
The direction of the magnetic force is perpendicular to the plane containing the velocity vector V and the magnetic field vector B.
5. A capacitor ‘C’, a variable resistor ‘R’ and a bulb ‘B’ are connected in series to the ac mains in circuit as shown. The bulb glows with some brightness. How will the glow of the bulb change if (i) a dielectric slab is introduced between the plates of the capacitor, keeping resistance R to be the same; (ii) the resistance R is increased keeping the same capacitance?
Solution: (i) As the dielectric slab is introduced between the plates of the capacitor, its capacitance will increase. Hence, the potential drop across the capacitor will decrease (V=QC). As a result, the potential drop across the bulb will increase (since both are connected in series). So, its brightness will increase.
(ii) As the resistance (R) is increased, the potential drop across the resistor will increase. As a result, the potential drop across the bulb will decrease (since both are connected in series. So, its brightness will decrease.
6. A proton and a deuteron are accelerated through the same accelerating potential. Which one of the two has
(a) greater value of de-Broglie wavelength associated with it, and
(b) less momentum?
Give reasons to justify your answer.
Solution: (a) de-Broglie wavelength, λ∝1 mass (for same accelerating potential)
Mass of a proton is less as compared to a deuteron. So, it will have greater value of de-Broglie wavelength associated with it.
(b) Momentum, p∝mass (for same accelerating potential)
Mass of a deuteron is more as compared to a deuteron. So, it will have a greater value of momentum.
7. When Sunita, a class XII student, came to know that her parents are planning to rent out the top floor of their house to a mobile company she protested. She tried hard to convince her parents that this move would be a health hazard.
Ultimately her parents agreed:
(a) In what way can the setting up of transmission tower by a mobile company in a residential colony prove to be injurious to health?
(b) By objecting to this move of her parents, what value did Sunita display?
(c) Estimate the range of e.m. waves which can be transmitted by an antenna of height 20 m. (Given radius of the earth = 6400 km)
Solution: (a) A transmitting tower makes use of electromagnetic waves such as microwaves, exposure to which can cause severe health hazards like tumour and cancer. Also, the transmitting antenna operates on a very high power, so the risk of someone getting severely burnt in a residential area increases.
(b) By objecting to this move of her parents, Sunita has displayed awareness towards the health and environment of her society.
(c) Range of the transmitting antenna, d = 2hR
Here, h is the height of the transmitting antenna and R is the radius of the Earth.
R = 6400 km = 64 ×105 m
d = 2×20×64×105d = 16000 m ans
CBSE Question Papers 2014 Reviews with Marking Instructions and Criteria
Many candidates are asking for loosely checking of paper however CBSE will follow its rule. All steps marking rules will be followed while checking the answer sheets. The paper was lengthy and many sets were arranged during examinations. Candidate can check solutions from here and many other websites have provided answer keys and solutions for CBSE 12th Board Physics Paper 2014.
If any other official circular regarding CBSE Physics Paper is reveals by CBSE regarding evaluations of marks sheet soon it will be updated here. The marking schemes are still same no any changes are going to be adopted to check Physics answer sheets of 2013-14.
Candidates must have to keep patience till their declaration results to check their exact marks and results of Physics. CBSE only advice to clear your further papers of 12th Board exams. Chemistry and Mathematics exams are ahead so prepare well for it. Both these subjects are very important from knowledge as well as percentage point of view.
We again suggest all CBSE 12th aspirants that doing better with good percentage is only an option to choose your better fields in future career. Concentrate on your exam and score well.
****Best of Luck for all CBSE EXAMS 2014****
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Also Check – CBSE Biology Model Test Papers 2014