CBSE 12TH PHYSICS - Online Test
Q1. In circuits, a difference in potential from one point to another is often called
Answer : Option A
Explaination / Solution:
Voltage is the common term used for potential difference or e m f.
Q2. Lorentz Force generally refers to
Answer : Option C
Explaination / Solution:
A moving charge experiences a force in a magnetic field called magnetic Lorentz force given by
Q3. According to the mirror equation
Answer : Option B
Explaination / Solution:
No Explaination.
Q4. Relation between atomic number (Z), neutron number (N) and mass number (A) is
Answer : Option C
Explaination / Solution:
mass number (A) = total number of nucleons = number of protons + number of nutrons = atomic number (Z) + neutron number (N).
Q5. In a potentiometer experiment, for measuring internal resistance of a cell, the balance point has been obtained on the fourth wire. The balance point can be shifted to fifth wire by
Answer : Option B
Explaination / Solution:
If the current due to the auxillary battery is decreased, the potential gradient will be decreases, so the balancing length increases.
Thus null point will move to fifth wire.
Q6. A ray is an imaginary
Answer : Option D
Explaination / Solution:
No Explaination.
Q7. In which case of comparing solenoid and bar magnet there is no exact similarity?
Answer : Option B
Explaination / Solution:
No Explaination.
Q8. In a pure, or intrinsic, semiconductor, valence band holes and conduction-band electrons are always present
Answer : Option A
Explaination / Solution:
An intrinsic semiconductor, also called an undoped semiconductor or i-type semiconductor, is a pure semiconductor without any significant dopant species present. The number of charge carriers is therefore determined by the properties of the material itself instead of the amount of impurities. In intrinsic semiconductors the number of excited electrons and the number of holes are equal: n = p.
Q9. The magnetic field of a plane electromagnetic wave travelling in +ve z direction is described by
Answer : Option D
Explaination / Solution:
No Explaination.
Q10. Magnetic flux (ΦB) through a surface S is given by
Answer : Option D
Explaination / Solution:
if dS is area of an element of any arbitrary shape and magnetic field at this element is B.
The total magnetic flux through the surface is the sum of the contributions from the individual area elements.
