Subject

Physics

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

21.

A coil of resistance 400 is placed in magnetic field. If the magnetic flux Φ (Wb) linked with the coil varies with time t  (sec) as Φ = 50t2 +4.
The current in the coil at t= 2 s is

  • 0.5 A

  • 0.1 A

  • 2 A

  • 2 A

1437 Views

22.

Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2I, respectively. The resultant magnetic field induction at the centre will be

  • fraction numerator square root of 5 straight mu subscript straight o straight I over denominator 2 straight R end fraction
  • fraction numerator 3 straight mu subscript straight o straight I over denominator 2 straight R end fraction
  • fraction numerator straight mu subscript straight o straight I over denominator 2 straight R end fraction
  • fraction numerator straight mu subscript straight o straight I over denominator 2 straight R end fraction
740 Views

23.

The potential energy of a particle in a force field is,straight U space equals straight A over straight r squared minus straight B over straight r where A and B are positive constants are r is the distance of a particle from the centre of the field. For stable equilibrium, the distance of a particle is

  • B/2A

  • 2A/B

  • A/B

  • A/B

534 Views

24.

In an electrical circuit R, L, C and AC voltage source are all connected in series when L is removed from the circuit, the phase difference between the voltage and the current in the circuit is π/3. If instead, Cis removed from the circuit, the phase difference is again π/3. The power factor of the circuit is

  • 1/2

  • 1 divided by square root of 2
  • 1

  • 1

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25.

A millivoltmeter of 25 mV range is to be converted into an ammeter of 25 A range. The value (in ohm) of necessary shunt will be

  • 0.001

  • 0.01

  • 1

  • 1

1263 Views

26.

A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. it

  • will become rigid showing no movement

  • will stay in any position

  • will stay in the north-south direction only

  • will stay in the north-south direction only

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27.

The electric field associated with an electromagnetic wave in vacuum is given by E=i 40 cos (kz-6x108t), where E, z= and t are in volt/m, metre and second respectively. The value of wave vector k is

  • 2 m-1

  • 0.5 m-1

  • 6 m-1

  • 6 m-1


A.

2 m-1

Electromagnetic wave equation 
straight E space equals space straight E subscript straight o space cos space left parenthesis kz minus ωt right parenthesis
Speed space of space electromagnetic space wave space straight v space equals space straight omega over straight k
space Given space equation
straight E space equals space straight i 40 space cos space left parenthesis kz minus 6 space straight x space 10 to the power of 8 space straight t right parenthesis
comparing space Eqs. space left parenthesis straight i right parenthesis space and space left parenthesis ii right parenthesis comma space we space get
straight omega space equals space 6 space straight x space 10 to the power of 8
and
straight E subscript straight o space equals 40 space straight i
here comma space wave space factor space straight k space equals space straight omega over straight v space equals space fraction numerator 6 space straight x space 10 to the power of 8 over denominator 3 straight x space 10 to the power of 8 end fraction space equals space 2 space straight m to the power of negative 1 end exponent

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28.

What is the flux through a cube of side a if a point charge of q is a one of its corner?

  • fraction numerator 2 straight q over denominator straight epsilon subscript straight o end fraction
  • fraction numerator straight q over denominator 8 straight epsilon subscript straight o end fraction
  • straight q over straight epsilon subscript straight o
  • straight q over straight epsilon subscript straight o
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29.

A ring is made of wire having a resistance Ro = 12Ω. Find the points A and B, as shown in the figure, at which a current carrying conductor should be connected so that the resistance R of the subcircuit between these points is equal to 8/3Ω

  • straight l subscript 1 over straight l subscript 2 space equals 5 over 8
  • straight l subscript 1 over straight l subscript 2 space equals space 1 third
  • straight l subscript 1 over straight l subscript 2 space equals space 3 over 8
  • straight l subscript 1 over straight l subscript 2 space equals space 3 over 8
872 Views

30.

If voltage across a bulb rated 220 V -100W drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is

  • 20%

  • 2.5%

  • 5%

  • 5%

552 Views

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