CBSE 12TH PHYSICS - Online Test
Q1. wave front is
Answer : Option D
Explaination / Solution:
a locus of points, which oscillate in phase is called a wavefront; thus a wavefront is defined as a surface of constant phase. The speed with which the wavefront moves outwards from the source is called the speed of the wave.
Q2. Which of the following statements about magnetic field lines true?
Answer : Option D
Explaination / Solution:
No Explaination.
Q3. Hole is a vacancy or lack of an electron and can travel through the semiconductor material. It can
Answer : Option C
Explaination / Solution:
Holes and electrons are the two types of charge carriers responsible for current in semiconductor materials.
Holes in a metal or semiconductor crystal lattice can move through the lattice as electrons can, and act similarly to positively-charged particles. They play an important role in the operation of semiconductor devices such as transistors, diodes and integrated circuits. However they are not actually particles, but rather quasiparticles; they are different from the positron, which is the antiparticle of the electron.
Q4. The electric field of a plane electromagnetic wave travelling in +ve z direction is described by
Answer : Option C
Explaination / Solution:
No Explaination.
Q5. Coils and are stationary. connected in series with a galvanometer while is connected to a battery through a tapping key. If the tapping key is pressed and released the galvaometer
Answer : Option C
Explaination / Solution:
flux will be changed when current in C2 is changing. Hence current will be induced in coil C1.
Q6. Photoelectric effect is possible
Answer : Option D
Explaination / Solution:
Emission of photoelectron takes place when energy of incident photon is greater than that of work function of material. Work function is different for different material. Photoelectric effect takes place for both UV and visible light depending on work function.
Q7. Which of these is an example of point to point communication?
Answer : Option C
Explaination / Solution:
In point to point communication,communication occurs over a link between a single transmitter and receiver.Telephony is an example of it as it needs a link between caller and receiver to transmit the information.This link is provided by various media like cable.
Q8. Electric charges are of
Answer : Option C
Explaination / Solution:
Two types
- Positivecharge—deficiency of electrons i.e. if a body loses electrons it will be positive charged.
- Negative charge—excess of electrons i.e. if a body gains electrons it will be negative charged
Q9. Which of these statements correctly describe the atomic model according to classical electromagnetic theory ?
Answer : Option B
Explaination / Solution:
No Explaination.
Q10. In a circuit containing Resistance only, voltage and current are
Answer : Option A
Explaination / Solution:
The electrical current that flows through an AC resistance varies sinusoidally with time and is represented by the expression, I(t) = I sin(ωt + θ)
Now by ohm's law, V= IR
So, for the AC circuit, V= IR sin(ωt + θ)
Clearly both V and I have zero phase difference and hen are in phase
