Physics - Online Test

Q1. About 5% of the power of a 100 W light bulb is converted to visible radiation. What is the average intensity of visible radiation at a distance of 1m from the bulb and at a distance of 10 m are
Answer : Option A
Explaination / Solution:
No Explaination.


Q2.
1.If an electron moving with a speed of 2.5 is deflected by an electric field of 1.6 k V perpendicular to its circular path, then e/m for the electron will be (given radius of circlar path = 2.3 m)

Answer : Option C
Explaination / Solution:

Electric field provide required centripetal force for circular motion


Q3. Space wave propagation can be
Answer : Option A
Explaination / Solution:
No Explaination.


Q4.

A ball is thrown upwards with an initial velocity of 10 m . Determine the maximum height reached above the thrower’s hand. Determine the time it takes the ball to reach its maximum height.


Answer : Option C
Explaination / Solution:

Initial velocity u = 10m/s

As at the maximum height ball ll stop so final velocity v = 0 m/s

Only acceleration working on it is acceleration due to gravity g = -9.8m/s​​​​​​2

Let height = h

So we know


=>

=> h= 5.10 m

Also let time taken to reach maximum height = t

Then 

We know 

v = u +at

=> 0 = 10 +(-9.8)t

=> t = 


Q5. Consider a uniform electric field (a) What is the flux of this field through a square of 10 cm on a side whose plane is parallel to the yz plane? (b) What is the flux through the same square if the normal to its plane makes a angle with the x-axis? 
Answer : Option D
Explaination / Solution:

(a) Electric field intensity, = 3 ×  î N/C Magnitude of electric field intensity, =  N/C Side of the square, s = 10 cm = 0.1 m Area of the square, A =  = 0.01  The plane of the square is parallel to the y-z plane. Hence, angle between the unit vector normal to the plane and electric field, θ= 0° Flux (Φ) through the plane is given by the relation, ϕ =  .  =3 ×  × 0.01 × cos0° = 30 N 
Q6. A specimen of oil having an initial volume of 600  is subjected to a pressure increase of 3.6   Pa and the volume is found to decrease by 0.45 cm3 what is the compressibility of the material?
Answer : Option B
Explaination / Solution:
No Explaination.


Q7. A 1.0-mol sample of an ideal gas is kept at 0.0C during an expansion from 3.0 L to 10.0 L. If the gas is returned to the original volume by means of an isobaric process, how much work is done by the gas?
Answer : Option A
Explaination / Solution:



Q8. A man of mass 70 kg stands on a weighing scale in a lift which is freely falling under gravity. What would be the reading on the scale?
Answer : Option D
Explaination / Solution:

When the lift fall freely under gravity, a = g

Therefore Apparent weight, (We experience weight due to reaction)


This is the condition for weightlessness.


Q9.

The Sun converts an enormous amount of matter to energy. Each second, 4.19 ×  kg—approximately the capacity of 400 average-sized cargo ships—is changed to energy. What is the power output of the Sun?


Answer : Option D
Explaination / Solution:

Energy liberated per second 


power output of sun is equal to energy output per second 


Q10. n accordance with the Bohr’s model, find the quantum number that characterises the earth’s revolution around the sun in an orbit of radius 1.5  m with orbital speed 3  m/s. (Mass of earth= 6.0  kg.)
Answer : Option C
Explaination / Solution:
No Explaination.