Physics - Online Test
Q1. A particle is executing S.H.M of amplitude a with a time period T sec. The time taken by it to move from positive extreme position to half the amplitude is
Answer : Option C
Explaination / Solution:
No Explaination.
Q2. Monochromatic light of wavelength 589 nm is incident from air on a water surface. What is the wavelength and speed of refracted light? Refractive index of water is 1.33.
Answer : Option D
Explaination / Solution:
No Explaination.
Q3.
A closely wound solenoid of 800 turns and area of cross section carries a current of 3.0 A. What is its associated magneticm oment?
Answer : Option D
Explaination / Solution:
No Explaination.
Q4. A beam of electrons at rest is accelerated by a potential V. This beam experiences a force F in a uniform magnetic field. The accelerating potential is changed to V’ and the force experienced by the electrons in the same magnetic field is 2F. The ratio V/V’ is
Answer : Option C
Explaination / Solution:
The energy of the electron after being accelerated by a potential V is v is the velocity of the electron.The force it experiences in a magnetic field B is When accelerated by a potential V’, the velocity is and the force in the same magnetic field is
Q5. The number of junctions in a transistor is/are
Answer : Option C
Explaination / Solution:
A transistor consisting of two p-n junctions combined to form either an n-p-n or a p-n-p transistor, having the three electrodes, the emitter, base, and collector
Q6. A jet lands on an aircraft carrier at 60 m/s. It stops in 2.0 s? What is the displacement of the plane in m while it is stopping?
Answer : Option D
Explaination / Solution:
Initial velocity u = 60 m/s
As it stops so final velocity v = 0 m/s
Time taken t = 2 seconds
We know
v-u = at
Also
From (1), we have
After putting given values, we have
=> s = 120-60 = 60 m
Q7. A whistling engine is approaching a stationary observer with velocity 110m/s. The velocity of sound is 330 m/s. The ratio of frequencies as heard by observer at the time of approaching and passing of engine is
Answer : Option A
Explaination / Solution:
No Explaination.
Q8. An air-cored solenoid with length 30 cm, area of cross-section 25 and number of turns 500, carries a current of 2.5 A. The current is suddenly switched off in a brief time of s. Average back emf induced across the ends of the open switch in the circuit is
Answer : Option A
Explaination / Solution:
ϕ=NBA=μ0N2Ail|e|=dϕdt
Q9. Use the formula T = 0.29 cmK to obtain the characteristic temperature range for m
Answer : Option C
Explaination / Solution:
No Explaination.
Q10.
If an electron accelerated from rest through a potential of 200 V acquires a speed of 8.4, then its e/m is
Answer : Option B
Explaination / Solution:
eV0=12mv2em=v22V0=(8.4×106)22×200=1.76×1011CKg−1
