Physics - Online Test
Q1. A metallic rod of 1 m length is rotated with a frequency of 50 rev/s about an axis passing through the centre point O. Other end of the metallic rod slides on a Metallic ring . A constant and uniform magnetic field of 2 T parallel to the axis is present everywhere. What is the emf between the centre and the metallic ring?
Answer : Option B
Explaination / Solution:
B = 2T
n = 50 rev/sec
l = 1m
Q2. Number of ejected photoelectrons increases with increase
Answer : Option D
Explaination / Solution:
No Explaination.
Q3. If a film of width L is stretched in the longitudinal direction a distance d by force F, surface tension is given by
Answer : Option D
Explaination / Solution:
Let L be the width of the film. Since the film has two surfaces, the total length along which the surface force acts on the slider is 2L. The surface tension S in the film is defined as the ratio of the surface force F to the length d (perpendicular to the force) along which the force acts
Hence, in the case, d = 2L
Q4. Fourier analysis of a periodic signal implies
Answer : Option A
Explaination / Solution:
The concept is that there are two descriptions of a signal according to Fourier. The time domain in form of time waveform and the frequency domain form in form of a combination of complex periodic signal with frequency as a variable instead of t. Hence Fourier analysis of a periodic signal implies periodic signal can be regarded as a superposition of sine wave signals
Q5. Rain is falling vertically with a speed of 30 m . A woman rides a bicycle with a speed of 10 m in the north to south direction. What is the direction in which she should hold her umbrella?
Answer : Option C
Explaination / Solution:
The described situation is shown in the given figure.
Here,
vc = Velocity of the cyclist
vr = Velocity of falling rain
In order to protect herself from the rain, the woman must hold her umbrella in the direction of the relative velocity (v) of the rain with respect to the woman.
v = vr + (-vc)
= 30 + (-10) = 20 m/s
tan θ =
θ = tan-1
Q6. A cylinder of radius R and length L is placed in an uniform electric field E parallel to the cylinder axis. The total flux for the surface of the cylinder is given by
Answer : Option B
Explaination / Solution:
Incoming flux =outgoing flux so net flux=0
Q7. Figure shows the strain-stress curve for a given material. What is the Young’s modulus?
Answer : Option D
Explaination / Solution:
No Explaination.
Q8. What amount of heat must be supplied to 2.0 kg of nitrogen (at room temperature) to raise its temperature by 45 C at constant pressure? (Molecular mass of = 28; R = 8.3 J
.)
.)
Answer : Option A
Explaination / Solution:
Q=nCvΔT=2×10−2×10−328×72×8.3×45=934Jn=wtingmMolecularwtCv=72RforDiatomicGas
Q9. Suppose you are given a chance to repeat the alpha-particle scattering experiment using a thin sheet of solid hydrogen in place of the gold foil. (Hydrogen is a solid at temperatures below 14 K.) What results do you expect?
Answer : Option A
Explaination / Solution:
No Explaination.
Q10. A body constrained to move along the z-axis of a coordinate system is subject to a constant force F given by , wher are unit vectors along the x-, y- and z-axis of the system respectively. What is the work done by this force in moving the body a distance of 4 m along the z-axis?
Answer : Option D
Explaination / Solution:
given that
