physics objective questions and answers

Physics : Multiple-Choice Questions

Physics : Multiple-Choice Questions

**Direction:**In the following questions more than one of the answers given may be correct. Select the correct answer and mark it according to the code.

**Code**:

(a) 1 and 2 are correct

(b) 2 and 3 are correct

(c) 1 and 4 and correct

(4)1, 2 and 4 are correct

1. In the case of projectile motion of two projectiles, A and B are projected with the same speed at angles 15° and 75° respectively to the horizontal, then:

(l) H

_{A}<H_{B}(2) H

_{A}> H_{B}(3) T

_{A}> T_{B}(4) T

_{A}< T_{B}Ans. (c)

_{ }2. A block is suspended by an ideal spring of force constant k. If the block is pulled down by applying a constant force F and if maximum displacement of block from its initial position of rest is δ then:

_{}

(l) F/k < δ < 2F/k

(2) δ = 2F/k

(3) Work done by the force is equal to F δ

(4) Increases in energy stored in spring is ½ k δ

^{2}Ans. (b)

3. The magnitudes of the gravitational field at distance r

_{1}and r_{2}from the centre of a uniform sphere of radius R and mass M are F1 and F2 respectively. Then:(1) F1/F2 = r

_{1/ }r_{2 }if r_{1 }<R and r_{2 }< R(2) F1/F2 = r

_{2}^{2}_{/ }r_{1}^{2}_{ }if r_{1 }>R and r_{2 }> R(3) F1/F2 = r

_{1/ }r_{2 }if r_{1 }>R and r_{2 }> R(4) F1/F2 = r

_{1}^{2}_{/ }r_{2}^{2}_{ }if r_{1 }<R and r_{2 }< RAns. (a)

4. Function x = A sin

^{2}ωt + B cos^{2}ωt + C sin ωt cos cot represents SHM:(1) For any value of 4, B and C (except C = 0)

(2) If A = -B, C = 2B, amplitude =|B√2|

(3) If A=B, C =2B, amplitude =|B|

(4) If A = B, C = 0

Ans. (b)

5. A wave disturbance in a medium is described by y(x, t) = 0.02 cos (50Πt +Π /2 )cos (10Πx), where x and y are in metre and t is in second?

(1) A node occurs at x = 0.15m

(2) An antinode occurs at x = 0.3 m

(3) The speed of wave is 15 ms

(4) The wavelength is 0.2 m

Ans. (d)

6. A bimetallic strip is formed act of two identical strips one of copper and the other of brass. The coefficients of linear expansion of the two metals are α

_{c}, and α_{β}. On heating, the temperature of the strip goes up by ΔT and the strip bends to form an arc of radius of curvature R. Then R is:(1) Inversely proportional to ΔT

(2) Proportional to |α

_{c -}α_{β }|(3) Proportional to ΔT

(4) Inversely proportional to| α

_{c -}α_{β}**|**Ans. (c)

7. For an ideal gas:

(1) The change in internal energy in a constant pressure process from temperature T1 and T2 is equal to nC

_{v}(T — T1), where C_{v}is the molar heat capacity at constant volume and n the number of moles of the gas(2) The change in internal energy of the gas and work done by the gas are equal in magnitude in an adiabatic process

(3) The internal energy increases in an isothermal process

(4) No heat is added or removed in an adiabatic process

Ans. (d)

8. A body of mass M is attached to the lower end of a metal wire, whose upper end is fixed. The elongation of the wire is l.

(1) Loss in gravitational potential energy of M is Mgl

(2) The elastic potential energy stored in the wire is 1/2 Mgl

(3) The elastic potential energy stored in the wire is Mgl

(4) Heat produced is Mgl

Ans. (d)

9. When a metal plate is introduced between the two plates of a charged capacitor and insulated from them, then:

(1) The metal plate divides the capacitor into two capacitors connected in parallel to each other

(2) The metal plate divides the capacitors into two capacitors connected in series with each other

(3) The metal plate is equivalent to a dielectric of infinite dielectric constant

(4) The metal plate is equivalent to a dielectric of zero dielectric constant

Ans. (b)

10. A parallel plate air capacitor is connected to a battery The quantities charge, voltage, electric field and energy associated with the capacitor are given by Q0, V0, E0 and U0 respectively. A dielectric slab is now introduced to fill the space between the plates with the battery 1still in connection. The corresponding quantities now given by Q, V, E and U related to the previous one as:

(1) Q>Q

_{0}(2) V>V

_{0}(3) E>E

_{0}(4) U>V

_{0 }Ans. (c)

11. Two identical double convex lenses each of the focal length ƒ is made of glass of μ== 1.5. If R is the radius of curvature of each of the four faces. Then:

(1) The focal length of combination is half the radius of curvature of any of the four faces

(2) The focal length of combination increases if the lenses are separated by a distance f and the new focal length is twice its focal length when the lenses are in contact

(3) The focal length of combination decreases when the lenses are separated by a distance ƒ and the new focal length is half its focal length when the lenses are in contact

(4) None of the above

Ans. (a)

12. Two resistors when connected in series have an equivalent resistance of 9 Ω and when connected in parallel have an equivalent resistance of 2 Ω. The value of these resistance of are

(1) 2Ω and 9Ω

(2) 3Ωand 6Ω

(3) 6Ω and 3Ω

(4) 3Ω and 9Ω

Ans. (b)

13. CapacitorC

_{1}of capacitance 1μF and capacitorC_{2}of capacitance 2μF are separately charged fully by a common battery. The two capacitors are then separately allowed to discharge through equal resistors at time t = 0.(1) The currents in the two discharging circuits at t=0 are equal but not zero

(2) The current in each of the two discharging circuits is zero at t = 0

(3) The current in the two discharging circuits at t = 0 are unequal

(4) Capacitor C

_{1}, losses 50% of its initial charge sooner than C_{2}losses 50% of its initial chargeAns. (c)

14. When photons of energy 4.25 eV strike the surface of a metal A, the ejected photoelectrons have maximum kinetic energy. T

_{A}expressed in eV and the de-Broglie wavelength λ_{A }. The maximum kinetic energy of photoelectrons liberated from another metal B by photons of energy 4.70 eV is T_{B}= ( T_{B}—1.5 eV). If the de-Broglie wavelength of these photoelectrons IS λ_{B}= λ_{A}then:(1) The work function of A is 2.25 eV

(2) The work function of B is 4.20 eV

(3) T = 2.7 eV

(4) TA= 2.00eV

Ans. (d)

15. Let λ

_{α}, λ_{β}and λ_{α’ }a denote the wavelength of the X-rays of the K_{α}, K_{β}and L_{α}lines in the characteristics, X-rays for a metal:(1) λ

_{α}> λ_{β}> λ_{α}‘(2) λ

_{α}> λ_{α’}> λ_{β}(3) λ

_{β}= 1/ λ_{α}+ 1/ λ_{α’}(4) 1/λ

_{α}+ 1/ λ_{β}= 1/ λ_{α’}Ans. (b)

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