CBSE 12TH PHYSICS - Online Test

Q1. work function of a metal is the
Answer : Option B
Explaination / Solution:

When the light strikes on a metal surface, electrons on the surface of the metal get energy from the light and get emitted from the surface. There will be no photoemission from a metal surface below a certain frequency of light. For photoemission minimum frequency of incident light is required. This minimum energy of an electron is called work function.

Q2. Electronic communication refers to
Answer : Option B
Explaination / Solution:

When information are sent from one point to the other it has to be converted into electrical signal using transducer.The receiver receives it in its original from using receiver.Such from of communication is called electronic communication.

Q3. Which of the following methods can be used to charge a metal sphere positively without touching it . Select the best
Answer : Option C
Explaination / Solution:

This can be possible by induction, if a negative charge rod is placed near the sphere (at a distance not in touch) than it attracts positive charge inside the sphere towards its side and the negative charges collected on other side and when the surface of sphere connected to earth than the negative charge goes to earth and the sphere remain positively charged.


Q4. According to ‘plum pudding model’ atoms on the whole are electrically neutral because
Answer : Option C
Explaination / Solution:
No Explaination.


Q5. Domestic power supply in India is
Answer : Option B
Explaination / Solution:

The standard voltage and frequency of alternating current supply in India is set to 220 V and 50Hz respectively by the government of India because when power has to be transmitted from a power plant, the biggest challenge is to cut the transmission losses. For this purpose, the current value should be small and potential difference(Voltage) should be more. Also losses are minimal at 50 Hz/60 Hz frequency.

Q6. Electric potential energy of two point charges q and q0 is 
Answer : Option B
Explaination / Solution:

Potential energy of a system of charges is the work done in assembling the charges. Force between two charges q and q0 placed at a distance r apart is Potential energy of the charges is given by
Q7. What is the unit of mass when measured on the atomic scale?
Answer : Option D
Explaination / Solution:

The unified atomic mass unit (u) is defined as one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest.

Q8. According to Cartesian sign convention.
Answer : Option C
Explaination / Solution:
No Explaination.


Q9. Which of the following is most general charachteristic of Magnetic field
Answer : Option A
Explaination / Solution:

A moving charge experiences a force in a magnetic field called magnetic Lorentz force given by.This force acts only if the particle (i) has charge q(ii) has a non zero velocity v and (iii) does not move parallel or anti parallel to the magnetic field B. A current carrying conductor placed in a magnetic field experiences a force given by
Q10. Two cells of 1.25 V and 0.75 V are connected in series with anode of one connected to anode of the other . The effective voltage will be
Answer : Option B
Explaination / Solution:

The cells are in opposition.