# HBSE Class 12 Physics Question Paper 2019 Answer Key

HBSE Class 12 Physics Question Paper 2019 Answer Key

HBSE Class 12 Physics Previous Year Question Paper with Answer. HBSE Board Solved Question Paper Class 12 Physics 2019. HBSE 12th Question Paper Download 2019. HBSE Class 12 Physics Paper Solution 2019. Haryana Board Class 12th Physics Question Paper 2019 Pdf Download with Answer.

SET-A

Q1.(i) Process of sharing the charges with the earth is called as ……………

Ans. Grounding or Earthing

(ii) SI unit of ∈⁰ (permitivity of free space) is :

(A) C-²N¹m-²

(B) C²N-¹m-²

(C) N¹C²m-²

(D) N-¹C²m²

Ans. (B) C²N-¹m-²

(iii) Write the expression for energy density of electric field ‘E’ in free space.

Ans. ½∈⁰E²

(iv) With the increase of temperature, the resistivity of a semiconductor :

(A) Decreases

(B) increases

(C) May increase or decrease

(D) Does not change

Ans. (A) Decreases

(v) How much current flows through a 2kΩ resistor when a potential difference of 4V is applied across its ends ?

Ans. Current, I = V/R = 4V/2kΩ = 4/2×10-³ = 2×10-³ A = 2 mA

(vi) What is the value of relative magnetic permeability of perfectly diamagnetic substance ?

Ans. Zero

(vii) The power factor for a purely capacitive circuit is :

(A) 1

(B) √2

(C) 1/√2

(D) Zero

Ans. (D) Zero

(viii) Which electromagnetic wave are used in cellular phones to transmit voice communication in the Ultra High Frequency (UHF) band ?

(ix) Who discovered the nucleus ?

(A) Thomson

(B) Bohr

(C) Rutherford

(D) de Broglie

Ans. (C) Rutherford

(x) What is SI unit of activity of Radioactive Substance ?

Ans. Becquerel or Bq

(xi) Rainbow is a phenomenon due to :

(A) Reflection

(B) Refraction

(C) Dispersion

(D) All of these

Ans. (D) All of these

(xii) What is the shape of wavefront for the light diverging from a point source ?

Ans. Spherical Wavefront

(xiii) Name the optoelectronic device used to detect optical signals.

Ans. Photo Detector

(xiv) In an electronic communication system, what is Attenuation ?

Ans. The loss of strength of a signal while propagating through a medium is called as Attenuation.

Q2. Three capacitors of capacitances 2 pF, 3 pF and 4 pF are connected in parallel. Determine the charge on each capacitor, if the combination is connected to a 100 V supply ?

Ans. Q = CV

Q1 = C1V = 2pF × 100 V = 2 × 10-¹⁰ coulomb

Q2 = C2V = 3pF × 100 V = 3 × 10-¹⁰ coulomb

Q3 = C3V = 4pF × 100 V = 4 × 10-¹⁰ coulomb

Q3. What is Kirchhoff’s loop rule ?

Ans. Kirchoff’s loop sale states that the algebric sum of changes in potential around a closed loop involving resistors and cells in the loop is zero.

Q4. Name four applications of Eddy currents.

Ans. Applications of Eddy currents-

(i) Magnetic breaking in trains

(ii) Electromagnetic damping

(iii) induction furnace

(iv) Electric power meters

Q5. State Faraday’s Law of Electromagnetic Induction.

Ans. When magnetic flux linked with coil changes, e.m.f is induced.

e.m.f. induced is equal to negative rate of change in Magnetic flux

Q6. A radio can tune into any station in the 7.5 MHz to 12 MHz band. What is corresponding wavelength band ?

Ans. Wavelength (λ) = C/v

λ1 = (3×10⁸m/s) ÷ (7.5×10⁶ Hz) = 40 m

λ= (3×10⁸m/s) ÷ (12×10⁶ Hz) = 25 m

So, corresponding wavelength band is 40 m to 25 m.

Q7. What is de Broglie wavelength of a bullet of mass 0.040 kg travelling at a speed of 1.0 km/sec ?

Ans. Broglie wavelength (λ) = h/mv = (6.6×10-³⁴) ÷ (0.040×1.0×10³m/s) = 1.6 × 10-³⁵ m

Q8. What is basic nuclear process underlying β- decay ? Write nuclear reaction of this decay for ²¹⁰Bi83.

Ans. Basic nuclear process in β- decay is

n → p + e- + v

²¹⁰Bi83 → ²¹⁰P84 + e- + v

Q9. Draw the I-V characteristics of a Zener diode. Also sketch the circuit diagram of Zener diode as a voltage regulator.

Ans. I-V Characteristics of Zener diode–

Zener diode as a Voltage Regulator–

Q10. Write the truth table for given circuit.

Ans. Truth table is

Q11. Draw Block diagram of Communication System.

Ans.

Q12. Discuss three basic postulates of Bohr’s model of atom.

Ans. Basic postulates of Bohr’s model of atom-

(i) In an atom, the electrons revolve around the nucleus in certain definite circular paths called orbits, or shells.

(ii) Each shell or orbit corresponds to a definite energy. Therefore, these circular orbits are also known as energy levels or energy shells.

(iii) The orbits or energy levels are characterized by an integer not, where, n can have values 1, 2, 3, 4……. The integer not (= 1, 2, 3…) is called the quantum number of respective orbit. The orbits are numbered as 1, 2, 3, 4………… etc., starting from the nucleus side. Thus, the orbit for which n=1 is the lowest energy level.

Q13. What is photoelectric effect ? Discuss the effect of intensity of light on photoelectric current.

Ans. The photoelectric effect refers to the emission, or ejection of electrons from the surface of a metal in response to incident light. This takes place because of the energy of incident photons of light have energy more than the work potential of the metal surface, ejecting electrons with positive kinetic energy. These electrons are used as the current and it is known as photo electric current.

Intensity has nothing to do with the energy of the photon.

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