Physics - Online Test

Answer : Option D
Explaination / Solution:

(i) Due to motion, the magnetic flux linked with the loop abcd increases. According to lenz's law this increase in flux is opposed by the induced current. Therefore, the induced current must flow anticlockwise

(ii) Due to motion, the magnetic flux linked with the loop abc decreases. So that induced current is clockwise.

(iii) Due to motion, the magnetic flux linked with the loop decreases. So that induced current is clockwise

Answer : Option B
Explaination / Solution:

maximum wavelength of visible light = 7700 A0

Energy

E=hcλ=6.6×10−34×3×1087700×10−10=2.57×10−19JE=2.56×10−191.6×10−19=1.6eV

Answer : Option A
Explaination / Solution:

The escape velocity is the minimum velocity required to leave a planet or moon. For a rocket or other object to leave a planet, it must overcome the pull of gravity.

Vescape=2GMR−−−−√

Vescape=11184 m/sec approximate to 11.2 km/sec

Answer : Option A
Explaination / Solution:

In electronics and telecommunications , modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. Most radio systems usea frequency modulation (FM) or amplitude modulation (AM) to make the carrier carry the radio broadcast.

Answer : Option C
Explaination / Solution:

In order to make vectors a + b + c + d = 0, it is not necessary to have all the four given vectors to be null vectors. There are many other combinations which can give the sum zero. (b) Correct a + b + c + d = 0 a + c = – (b + d) Taking modulus on both the sides, we get: | a + c | = | –(b + d)| = | b + d | Hence, the magnitude of (a + c) is the same as the magnitude of (b + d). (c) Correct a + b + c + d = 0 a = – (b + c + d) Taking modulus both sides, we get: | a | = | b + c + d | | a | ≤ | a | + | b | + | c | ..... (i) Equation (i) shows that the magnitude of a is equal to or less than the sum of the magnitudes of b, c, and d. Hence, the magnitude of vector a can never be greater than the sum of the magnitudes of b, c, and d. (d) Correct For a + b + c + d = 0 a + (b + c) + d = 0 The resultant sum of the three vectors a, (b + c), and d can be zero only if (b + c) lie in a plane containing a and d, assuming that these three vectors are represented by the three sides of a triangle. If a and d are collinear, then it implies that the vector (b + c) is in the line of a and d. This implication holds only then the vector sum of all the vectors will be zero.

Answer : Option A
Explaination / Solution:

For perfectly Inelastic collision coefficient of restitution is zero. coefficient of restitution e= relative velocity of separation / relative velocity of approach e = 0 so that relative velocity of separation will be zero means the colliding bodies stick together and move as one body after the collision

Answer : Option C
Explaination / Solution:

Electric field due to thin sheet— Let a thin sheet on which a charge q is distributed uniformly , let the Gaussian surface on both sides is in form of cylinder as shown in figure 


$\varphi$(left) + 
$\varphi$(right)=$ =EA Cos0+EA Cos0=2EA 

Answer : Option B
Explaination / Solution:
No Explaination.

Answer : Option B
Explaination / Solution:

Spontaneous processes are irreversible because they can be reversed only by taking a different path to get back to their original state. A reversible process can take the same path to return to its original state.

Answer : Option A
Explaination / Solution:
No Explaination.