Physics - Online Test
Q1. The units of pressure are the same as the units of
Answer : Option A
Explaination / Solution:
Pressure is not the same physical thing as stress, but they do use the same definition and thus produce the same units, so the same calculator can be used for both. They both measure force per unit area.
SI unit of both pressure and stress is Pascal.
Q2. Series LCR circuit is connected to a variable frequency 230 V source. L = 5.0 H, C = 80 μF, R = 40 Ω. Impedance of the circuit and the amplitude of current at the resonating frequency are
Answer : Option B
Explaination / Solution:
impedence in series LCR circuit
at resonance
hence
V = 230 Volt
Hence current
Q3. A milliammeter of range 10 mA has a coil of resistance 1 Ω.To use it as an ammeter of range 1 A, the required shunt must have a resistance of
Answer : Option C
Explaination / Solution:
(Theory in chapter 4 – magnetic effect of current)
(Theory in chapter 4 – magnetic effect of current)
Q4. A particle is executing simple harmonic motion with an amplitude of 0.02 meter and frequency 50 hertz. The maximum acceleration of the particle is
Answer : Option D
Explaination / Solution:
No Explaination.
Q5. If two stars have an angular separation of Δθ and ‘a’ is the radius of the telescope aperture, then the angular resolution (for the stars to appear separate) is given by the expression
Answer : Option C
Explaination / Solution:
No Explaination.
Q6. To increase the magnetic field of a solenoid what core material should be used ?
Answer : Option A
Explaination / Solution:
No Explaination.
Q7. The impurity atoms with which pure silicon should be doped to make a p-type semiconductor are those of
Answer : Option A
Explaination / Solution:
In a pure (intrinsic) Si or Ge semiconductor, each nucleus uses its four valence electrons to form four covalent bonds with its neighbors . Each ionic core, consisting of the nucleus and non-valent electrons, has a net charge of +4, and is surrounded by 4 valence electrons. Since there are no excess electrons or holes In this case, the number of electrons and holes present at any given time will always be equal. Note each +4 ion is surrounded by four electrons.
Now, if one of the atoms in the semiconductor lattice is replaced by an element with three valence electrons, such as a Group 3 element like Boron (B) or Gallium (Ga), the electron-hole balance will be changed.
This impurity will only be able to contribute three valence electrons to the lattice, therefore leaving one excess hole . Since holes will "accept" free electrons, a Group 3 impurity is also called an acceptor.
A semiconductor doped with an acceptor. An excess hole is now present. Because an acceptor donates excess holes, which are considered to be positively charged, a semiconductor that has been doped with an acceptor is called a p-type semiconductor.
Q8.
If the velocities of two particles A and B are respectively and velocity of object B relative to object A is
Answer : Option D
Explaination / Solution:
Relative velocity of a body A with respect to another body B, when both are in motion, is the velocity with which A appears to move to B.
In general,
Q9.
Beats arise when two waves having slightly different frequencies, and and comparable amplitudes, are superposed. The beat frequency is
Answer : Option B
Explaination / Solution:
No Explaination.
Q10.
Light with an energy flux of 18 W/ falls on a nonreflecting surface at normal incidence. If the surface has an area of 20 , Average force exerted on the surface during a 30 minute time span is
Answer : Option C
Explaination / Solution:
No Explaination.
