CBSE 12TH PHYSICS - Online Test
Q1. A potential difference of 220 V is maintained across 12000 rheostat. Then voltmeter V has a resistance of 6000 and point C is at one fourth the distance from a to b. Then the reading of voltmeter is
Answer : Option B
Explaination / Solution:
Resistance R = 1/4R = 12000/4 = 3000 parallel. .
This is in series with Rbc.
The current in the circuit I = 220/11000 = 0.02A The reading of the voltmeter is the potential drop across Rp. V = 0.02 * 2000 = 40V
This is in series with Rbc.
The current in the circuit I = 220/11000 = 0.02A The reading of the voltmeter is the potential drop across Rp. V = 0.02 * 2000 = 40V
Q2. Interference effects of light from two sources can be observed if
Answer : Option C
Explaination / Solution:
If the two sources are coherent, then the phase difference φ at any point will not change with time and we will have a stable interference pattern; i.e., the positions of maxima and minima will not change with time.
Q3. magnetic declination and dip refer to
Answer : Option B
Explaination / Solution:
No Explaination.
Q4. in p-type semiconductor the dopant is
Answer : Option D
Explaination / Solution:
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).
Q5. The speed of plane electromagnetic waves is maximum in
Answer : Option A
Explaination / Solution:
No Explaination.
Q6. A moving conductor rod is 0.10 m long, and moves with a velocity of 2.5 m/s perpendicular to the magnetic field B of 0.60 T. If the circuit is completed with a resistance of 0.03Ω. Find the motional emf and the induced current.
Answer : Option B
Explaination / Solution:
e = Bvl = 0.60 x 2.5 x 0.1 = 0.15V
Q7. According to the Einstein’s model stopping potential for a metal having work function ϕ0 is given by
Answer : Option A
Explaination / Solution:
eV0=KmaxKmax=hν−ϕ0eV0=hν−ϕ0V0=(he)ν−ϕ0e
Q8. In Analog type signals
Answer : Option B
Explaination / Solution:
A signal in which current or voltage varies with time is called analog signal.A vibrating fork produces such a sound signal of single frequency.Every speech or music is a complex signal formed by the superposition of several sinusoidal signals of different amplitudes and frequencies.
Q9. For charges separated by a distance R the magnitude of the electrostatic force is given by
Answer : Option D
Explaination / Solution:
According to Coulomb’s law the force between two point charges is
(a) The force is directly proportional to the product of magnitude of charges i.e.
(b) The force is inversly proportional to the square of distance between two charges i.e.
Combining both
OR
Where k is a constant of proportionality known as force constant having different value in different systems
Q10. Absorption line spectrum is obtained
Answer : Option B
Explaination / Solution:
No Explaination.
