Physics

Physics

1. A charged particle of mass m and charge q is released from rest in a uniform electric field E.The kinetic energy of the particle after time t is

Correct answer: (C)

2. In an ammeter 0.2 % of main current passes through the galvanometer. If resistance of galvanometer is G, the resistance of ammeter will be

Correct answer: (B)

3. The pressure exerted by an electromagnetic wave of intensity I (watt m-2) on a non-reflecting surface is [c is the velocity of light]

  1. Ic
  2. Ic2
  3. I/c
  4. I/c2

Correct answer: (C)
I/c

4. A beam of electrons is accelerated through a Potential difference V. It is then passed normally through a uniform magnetic field where it moves in a circle of radius r. It would have moved in a circle of radius 2r if it were initially accelerated through a Potential difference.

  1. √2 V
  2. 2V
  3. 2√2 V
  4. 4V

Correct answer: (D)
4V

5. A magnetic needle lying parallel to a magnetic field requires W units of work to turn it through 600 . The torque required to maintain the needle in this position is

  1. √3W
  2. W
  3. W
  4. 2W

Correct answer: (A)
√3W

6. A thin rod of length ‘L’ and mass ‘M’ held vertically with one and fixed on the floor is allowed to fall. The velocity of the other end when it hits the floor is

  1. √3gL
  2. √5gL
  3. √2gL
  4. √gL

Correct answer: (A)
√3gL

7. In a step-up transformer, the turns ratio of primary and secondary is 1:2 A leclanche cell of emf 1.5 V is connected a cross the primary. The voltage developed across the secondary would be

  1. zero
  2. 3.0 V
  3. 1.5V
  4. 0.75V

Correct answer: (A)
zero

8. Choose the correct option

  1. The radiation in increasing order of frequency are radio waves, micro waves, infrared, visible, ultraviolet, x-rays, gamma rays, cosmic rays.
  2. The wave length of colours in increasing order violet, indigo blue, green, yellow, orange and red
  3. The speed of light is maximum in vacuum .
  4. All options are correct.

Correct answer: (D)
All options are correct.

9. If the electron in a hydrogen atom jumps from the third orbit to the second orbit, the emitted radiation has wave length. (‘R’ is Rydberg’s constant).

Correct answer: (A)

10. Three-fourths of the active nuclei present in a radioactive sample decay in s. The half-life of the sample is

  1. 1 sec
  2. sec
  3. sec
  4. sec

Correct answer: (D)
sec