CBSE 12TH PHYSICS - Online Test
Q1. At resonance the current in an LCR circuit
Answer : Option D
Explaination / Solution:
in LCR series circuit current
at resonance
hence current will be maximum.
Q2. An equipotential surface is a surface
Answer : Option D
Explaination / Solution:
When the potential at all points on the surface is the same; such a surface is called an equipotential surface. The potential difference between any two points on an equipotential surface is zero, while the potential may be positive, negative or even zero.
Q3. The power P of a lens is given by the approximate formula
Answer : Option B
Explaination / Solution:
No Explaination.
Q4. Correct expression for mass defect Δm is
Answer : Option C
Explaination / Solution:
Measurements have shown that the mass of a particular atom is always slightly less than the sum of the masses of the individual neutrons, protons, and electrons of which the atom consists. The difference between the mass of the atom and the sum of the masses of its parts is called the mass defect.
Here Z is the number of protons (atomic number) and (A-Z) is the number of neutrons, A being the total number of nucleons (mass number).
Q5. The magnetic field at the center of a toroidal coil having n turns,radius r and carrying a current I in air is
Answer : Option B
Explaination / Solution:
A toroid is a solenoid wound on itself. The magnetic field exists only in the region of the hollow circular ring which has the turns of wire wound on it. Using Ampere’s circuital law,
Q6. The figure shows an unbalanced Wheatstone bridge. To balance the bridge:
Answer : Option B
Explaination / Solution:
To balance bridge
So X = 90
Q7.
If we have two coherent sources vibrating in phase with same amplitude, then for an arbitrary point P with path difference corresponding to , the resultant intensity if the intensity due to each is I0 would be
Answer : Option C
Explaination / Solution:
No Explaination.
Q8.
if =magnetic intensity, =susceptibility, magnetic moment per unit volume equals
Answer : Option A
Explaination / Solution:
No Explaination.
Q9. Diffusion in a p-n junction is due to
Answer : Option A
Explaination / Solution:
- In n-type semiconductor, the concentration of electrons is more compared to the concentration of holes. Similarly, in p-type semiconductor, the concentration of holes is more compared to the concentration of electrons
- The first process that occurs in the p-n semiconductor is diffusion
- In the formation of the p-n junction, due to the concentration gradient across the p and the n sides, the electrons diffuse from n region to p region and the holes diffuse from p region to n region.
Q10. Microwaves have a frequency of about
Answer : Option C
Explaination / Solution:
No Explaination.
