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12th Physics Objective Questions and Answers 2020 » allsarkariexams.com


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1. The unit for an electrical field is :

  • volt
  • Ampere
  • ohm
  • NC⁻¹
Ans: NC⁻¹

2. When a conductor is heated, its resistance :

  • Increases
  • decreases
  • remains constant
  • depends upon the nature of the conductor
Ans: Increases

3. The electrical potential at a point inside a charged spherical shell is :

  • Zero
  • Constant
  • Variable
  • Maximum

 

Ans: Zero

4. What is the SI unit of magnetic dipole moment :

  • Am²
  • Am
  • Am⁻²
  • None

Ans: Am²

Ans: Increases

5. Mention the S.I unit of a magnetic field :

  • gauss
  • Tesla
  • Weber
  • None
Ans: Tesla

6. Kirchoff loop rule is a direct consequence of low of conservation of :

  • Charge
  • Momentum
  • Angular Momentum
  • Energy
Ans: Energy

7. Lenz’s law is in accordance with the low of conservation of :

  • Momentum
  • Angular Momentum
  • Charge
  • Energy
Ans: Energy

8. Which of the Following can be Deflected by a magnetic field :

  • α – rays
  • β – rays
  • γ – rays
  • a & b Both
Ans: a & b Both

9. Name the electromagnetic radiation used for viewing objects through haze & fog :

  • Infrared
  • rays
  • x-rays
  • Microwaves None
Ans: Infrared

10. Which Colour of light gets deviated the most when sunlight passes through a prism :

  • Red
  • Yellow
  • Violet
  • Green

Ans: Violet

Ans: Increases





11. The radius of curvature of a mirror is 20 cm. What is its Focal length :

  • 5 cm
  • 10 cm
  • 20 cm
  • None
Ans: 10 cm

12. Electron & Proton are moving at the same speed. Which we having more Wavelength.

  • Electron
  • Proton
  • Both Have Same
  • None Of This
Ans: Electron

13. Which series of H-atom spectrum lies in the ultra-violet region :

  • Balmer series
  • Lyman series
  • Pascher series
  • None of this
Ans: Lyman series

14. What is Called Ratio Of Potential difference & Current :

  • Resistance
  • Resistivity
  • Conduction
  • none
Ans: Resistance

15. Electric current is Scalar or Vector :

  • vector
  • scalar
  • neither vector & scalar
  • none
Ans: scalar

16. If a wire stretched by a force, its resistance :

  • Increases
  • decreases
  • remains constant
  • None
Ans: Increases

17. The unit of electrical current density is :

  • Am²
  • Am
  • Am⁻²
  • Am⁻¹
Ans: Am⁻²

18. As temperature increases the conductivity of a semiconductor :

  • Increases
  • decreases
  • remains constant
  • None
Ans: Increases

19. Potential gradient has unit :

  • vm
  • vm⁻¹
  • vm⁻²
  • vm²
Ans: vm⁻¹

20. The SI unit for impedance is :

  • ohm

  • Henry
  • Volt
  • Ampere
Ans: ohm





21. The Caused of induced emf in a closed coil is :

  • Magnetic field
  • Magnetic flux
  • Rotation of coil
  • Change in Magnetic flux
Ans: Magnetic flux

s is :22. The absolute permeability of free space in S.I unit

  • 1⁄4π×₁₀⁻⁷
  • ₁₀⁻⁷
  • 4π×₁₀⁻⁷
  • 4π×₁₀⁷
Ans: 4π×₁₀⁻⁷

23. Which part of the electromagnetic spectrum is used in a radar system?

  • Ultraviolet
  • infrared
  • Radio waves
  • x rays
Ans: Radio waves

24. Critical Angle (C) and refractive index (µ) of medium are related as :

  • µ = sin c
  • µ = cos c
  • µ = tan c
  • µ = cosec c
Ans: µ = cosec c

25. MeV is the unit for :

  • Voltage
  • Current
  • Power
  • Energy
Ans: Energy

26. Farad is unit for :

  • Electric current
  • electric potential
  • Energy
  • capacitance
Ans: capacitance

27. A positively charged body has :

  • excess of electron
  • deficit of electrons
  • excess of proton
  • deficit of proton
Ans: excess of proton

28. As a temperature rises, the resistance of a conductor :

  • Increases
  • decreases
  • remains constant
  • depends upon the nature of the conductor
Ans: Increases

29. Zener diode is used for :

  • Oscillations
  • amplifications
  • rectification
  • voltage stabilization.
Ans: voltage stabilization

30. eV is a unit for :

  • potential difference
  • power
  • energy
  • momentum
Ans: energy

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