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# Physics Important Questions for Competitive Exams

1. The coulomb electrostatic force is defined for?
1) Two spherical charges at rest
2) two spherical charges in motion
3) two point charges in motion
4) two point charges at rest

2. The path of a charged particle projected into a uniform electric field is?
1) Circle
2) hyperbola
3) parabola
4) ellipse

3. Gauss’s law is true only if force due to a charge varies as?
1) r-1
2) r-2
3) r-3
4) r-4

4. A proton and an α- particle start from rest in a uniform electric field, then the ratio of times of flight to travel same distance in the field is?
1) √5: √2
2) √3: 1
3) 2 : 1
4) 1 : √2

5. The magnitude of the electric field on the surface of a sphere of radius r having a uniform surface charge density σ is?
1) σ/EO
2) σ/2EO
3) σ/EOr
4) σ/2EOr

6. if a hemispherical body is placed in a uniform electric field E. then the flux linked with the curved surface is?
1) 2πR2
E 2) πR2 E
3) 4πR2 E
4) 6πR2 E

7. An electric dipole kept in a uniform electric field experiences?
1) A force and a torque
2) a force but not a torque
3) a torque but not a force
4) neither a force nor a torque

8. The electric intensity E, and potential V on the perpendicular bisector of an electric dipole are?
1) E=0, V= 0
2) E≠0, V≠0
3) E≠0, V= 0
4) E= 0, V≠0

9. The capacity of parallel plate condenser depends on?
1) The type of metal used
2) the thickness of plates
3) the potential applied across the plates
4) the separation betwine the plates

10. The value of dielectric constant (K) in case of metals is?
1) One
2) infinity
3) zero
4) two

11. The potential at the origin is zero due to electric field E= 20i + 30i Nc-1. The potential at point p(2m1 2m)
1) IV
2) -100V
3) 10V
4) 2V

12. A charged sphere is connected a similar uncharged sphere then percentage loss of energy is?
1) 50 %
2) 25 %
3) 20 %
4) 10%

13. The capacity of parallel plate capacitor of each plate area of 10cm x 10 cm and separated by a distance 1mm?
1) 88.42 PF
2) 8 PF
3) 2PF
4) 10PF

14. n drops each of radius ‘r’ and carrying a charge ‘q’ are combined to form a bigger drop. The ratio of potentials of bigger to that of smaller is?
1) N3/2: 1
2) n1/3: 1
3) n2/3: 1
4) n3/4:1

15. A parallel plate capacitor has capacitance of 2µF and 12µF when immersed in oil the dielectric constant of the oil is?
1) 5
2) 4
3) 3
4) 6

16. The energy stored in the capacitor is?
1) ½ cv2
2) ½ QV2
3) ½.Q/C
4) ½ Q/C2

17. Drift velocity of free electrons is related to?
1) Under uniform electric filed
2) under non-uniform electric filed
3) under uniform magnetic field
4) under non-uniform magnetic field

18. According to ohm’s law the graph I versus V gives?
1) Straight line with Y-Intercept
2) straight line passing through origin
3) parabola with positive slope
4) None

19. If the temperature of the metallic conductors increases, then resistance of it is?
1) Increases
2) decreases
3) remain same
4) zero

20. Fuse wire is used in electrical power meters because It has?
1) High resistivity
2) low melting point
3) both
4) high melting point

21. The elements of heating devices are made up of?
1) Copper
2) aluminium
3) nichrome
4) tungsten

22. At absolute zero resistivity of any metal becomes?
1) Zero
2) infinity
3) no change
4) does not depend on temperature

23. Temperature coefficient of resistance is positive for?
1) Silver
2) silicon
3) carbon
4) electrolyte

24. Which one given bellow is an irreversible phenomena?
1) Coulomb’s law
2) Gauss’s law
3) Ohm’s law
4) Joule’s law

25. Five identical resistances of each 25 ohms are connected parallel than effective resistance is?
1) 3
2) 4
3) 5
4) 6

26. ‘n’ resistors cache of resistance R are first connected in series and then in parallel, the ratio of resistances in two cases?
1) n2:1
2) n:1
3) 1:n2
4) 1:n

27. For making standard resistance wire of following material is used
1) Nichrome
2) Copper
3) Silver
4) Manganin

28. To supply maximum current, cells should be arrange in
1) series
2) parallel
3) mixed grouping
4) depends on the internal & external resistance

29. Back emf of a cell is due to
1) Electrolytic polarisation
2) peltier effect
3) Magnetic effect
4) None

30. Kirchhoff’s laws are based on?
1) conservation of charge, conservation of energy
2) conservation of charge, conservation of momentum
3) conservation of energy, conservation of momentum
4) conservation of charge only

31. Three resistances 1Ω, 2Ω, 3Ω are connected in parallel. The ratio of currents passing through them when potential applied across the ends is
1) 2:3:6
2) 1:2:3
3) 1:1:1
4) 6:3:2

32. When two identical wires made of different materials having resistivities S1 and S2, Effective resistivity in series is?
1) (S1+S2)/2
2) S1+S2
3) 2(S1+S2)
4) S1 S2

33. current ‘i’ is flowing in hexagonal coil of side a the magnetic induction at the centre of the coil is?
1) 3√3 µoi/πa
2) µoi/3√3πa
3) µoi/√3πa
4) √3µoi/πa

34. A Wire of length ‘L’ meters carrying a current ‘i’ amperes is bent in the form of a circle. the magnitude of its magnetite moment is?
1) iL/4π
2) iL2 /4π
3) i2 L/4π
4) i2 L2 /4π

35. Which of the following are not accelerated by a cyclotron
1) proton
2) α – particle
3) newton
4) both 2 and 3