Physics - Online Test
Q1. Dielectric polarization is the phenomenon
Answer : Option C
Explaination / Solution:
Atomic dipoles in a dielectric experience a torque when placed in an external electric field. As a result of this torque, they align themselves in the direction of the electric field, since thi is the position of least potential energy. This phenomenon in which the atomic dipoles align themselves in the diorection of the electric field is called dielectric polarization.
Q2. Strong Nuclear Force is
Answer : Option A
Explaination / Solution:
In particle physics, the strong interaction is the mechanism responsible for the strong nuclear force (also called the strong force or nuclear strong force), and is one of the four known fundamental interactions, with the others being electromagnetism, the weak interaction and gravitation. At the range of 10−15 m (femtometer), the strong force is approximately 137 times as strong as electromagnetism, a million times as strong as the weak interaction and 1038times as strong as gravitation.
Q3. If the radius of earth contracts to half of its present value, the mass remaining unchanged, the duration of the day will be
Answer : Option C
Explaination / Solution:
As the Moment of inertia of earth considered as sphere is I = 2/5 MR2 , thus according to law of conservation of angular momentum as the radius contracts to half , thus new moment of inertia of earth will be I/4 , thus the angular velocity will increase 4 times and making the length of the day to 6 hrs.
Q4. A soap bubble has radius r and the surface tension of the soap film is T. The energy needed to double the diameter of the bubble without change of temperature is
Answer : Option D
Explaination / Solution:
No Explaination.
Q5. What is the average kinetic energy of the helium atoms in a balloon of diameter 30.0 cm at 20.0C and 1.00 atm?
Answer : Option B
Explaination / Solution:
K¯=32kT=32×1.38×10−23×293=6.07×10−21J
Q6. The equi-convex lens, show in the figure, has a focal length ƒ. What will be the focal length of each half if the lens it cut along AB?
Answer : Option A
Explaination / Solution:
No Explaination.
Q7. The mean binding energy per nucleon in the nucleus of an atom is nearly
Answer : Option C
Explaination / Solution:
No Explaination.
Q8.
A 10 kW drilling machine is used to drill a bore in a small aluminum block of mass 8.0 kg. How much is the rise in temperature of the block in 2.5 minutes, assuming 50 percent of power is used up in heating the machine itself or lost to the surroundings. Specific heat of aluminum = 0.91 J .
Answer : Option D
Explaination / Solution:
Energy used in heating = 50% =75 x 105J
Q9. The number of significant digits in 6.032 N is
Answer : Option B
Explaination / Solution:
There are three rules on determining how many significant figures are in a number:
- Non-zero digits are always significant.
- Any zeros between two significant digits are significant.
- A final zero or trailing zeros in the decimal portion ONLY are significant.
So keeping these rules in mind, there are 4 significant digit
Q10. Reactance of a 3.00-H inductor at a frequency of 80.0 Hz is
Answer : Option D
Explaination / Solution:
L = 3 H
f = 80 Hz
Inductive reactance
