CBSE 12TH PHYSICS - Online Test
Q1. The current in a series LCR circuit excited by AC of frequency ω is in general
Answer : Option D
Explaination / Solution:
The above expression is for instantaneous value of current in an AC Circuit and since in an LCR circuit current is same across the circuit, the above expression holds valid for the entire LCR series circuit.
Q2.
If R is the radius of a spherical conductor, the dielectric strength, maximum electric-field magnitude to which it can be raised is
Answer : Option A
Explaination / Solution:
Dielectric strength is the maximum electric field intensity the medium can bear without suffering a breakdown. The electric field intensity has a maximum value on the surface of the spherical conductor, therefore,
Q3. Lens maker’s formula is
Answer : Option D
Explaination / Solution:
No Explaination.
Q4. Nuclear mass M is found to be
Answer : Option D
Explaination / Solution:
This phenomenon is called mass defect. The mass defect of a nucleus represents the mass equivalent of the energy of binding of the nucleus, and is the difference between the mass of a nucleus and the sum of the masses of the nucleons of which it is composed.
Q5. According to Ampere's circuital law
Answer : Option A
Explaination / Solution:
the expression for Ampere’s circuital law is where I is the current included in the surface bounded by the line integral.
Q6. Figure shows current in a part of an electrical circuit. Then current I is
Answer : Option A
Explaination / Solution:
Using Kirchhoff’s junction rule at junction A,2 + 5 - 2 - 1 + IAB = 0;IAB = - 4A
The current IAB is directed away from the junction A. Using the junction rule at B 4 + 0.2 - 1.7 - I = 0;
I = 2.5A
Q7. If we have two coherent sources vibrating in phase, then for an arbitrary point P constructive interference is observed whenever the path difference is
Answer : Option B
Explaination / Solution:
No Explaination.
Q8.
magnetic intensity is defined by
Answer : Option B
Explaination / Solution:
No Explaination.
Q9. in p-type semiconductor
Answer : Option B
Explaination / Solution:
P-type semiconductors have a larger hole concentration than electron concentration. The term P-type refers to the positive charge of the hole.
In P-type semiconductors, holes are the majority carriers and electrons are the minority carriers. P-type semiconductors are created by doping an intrinsic semiconductor with acceptor impurities (or doping an n-type semiconductor).
A common P-type dopant for silicon is boron. For P-type semiconductors the Fermi level is below the intrinsic Fermi level and lies closer to the valence band than the conduction band.
Q10. Radio waves for FM radio have a frequency about
Answer : Option A
Explaination / Solution:
No Explaination.
