National Standard Examination in Physics (NSEP) Solved Paper 2016 Part-15

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Q: 51. The half- life period of a radioactive element is equal to the mean lifetime of another radioactive element Initially both the elements have the same number of atoms. Therefore,

(A) will decay faster

(B) will decay faster

(C) will decay at the same rate

(D) Data insufficient

Answer: (A)

Q: 52. An ac source (sinusoidal source with frequency 50 ) is connected in series with a rectifying diode, a 100 resistor, a 1000 capacitor and milliammeter. After some time the milliammeter reads zero. The voltage measured across the capacitor with a dc voltmeter is

(A) The peak voltage of the ac source

(B) rms voltage of the ac source

(C) Average voltage of the ac source over a half cycle

(D) Average voltage of the ac source over a full cycle

Answer: (C)

In this state the circuit will work as half wave rectifier and the voltage across capacitor will be equal to average value of voltage of ac source over a half cycle.

Q: 53. The frequency of the sound produced by a siren increases from 400 Hz to 1200 Hz while its amplitude remains the same. Therefore, the ratio of the intensity of the 1200 Hz wave to that of the 400 Hz wave is

(A)

(B)

(C)

(D)

Answer: (D)

Q: 54. The fundamental frequency of the output of a bridge rectifier driven by ac mains is

(A) 50 Hz

(B) zero

(C) 100 Hz

(D) 25 Hz

Answer: (C)

Q: 55. The force of attraction between the positively charged nucleus and the electron in a hydrogen atom is given by Assume that the nucleus is fixed. The electron, initially moving in an orbit of radius jumps into an orbit of smaller radius The decrease in the total energy of the atom is.

(A)

(B)

(C)

(D)

Answer: (C)

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