CBSE 12TH PHYSICS - Online Test
Q1. A rectangular conductor PQRS in which the conductor PQ is free to move is kept in a magnetic field B ,which is perpendicular to the PQRS which lies in a single plane. If the conductor PQ has a length l,moves with a speed v, then induced emf is
Answer : Option B
Explaination / Solution:
e=dϕdt=d(BS)dt=B.dsdt=Bl.dxdt=Blv
Q2. According to the Einstein’s model minimum energy needed for the electron to escape from a metal surface having work function , the electron is emitted with maximum kinetic energy =
Answer : Option D
Explaination / Solution:
When any photon is incident on a metal surface it gives its total energy to a electron. Some energy(Work Function) is used up in come out from the metal surface and remaining energy is kinetic energy of electron.
Q3. Any physical quantity like temperature can be converted to
Answer : Option A
Explaination / Solution:
An electrical transducer is a device which is capable of converting the physical quantity into a proportional electrical quantity such as voltage or electric current. Hence it converts any quantity to be measured into usable electrical signal. This physical quantity which is to be measured can be pressure, level, temperature, displacement etc. The output which is obtained from the transducer is in the electrical form and is equivalent to the measured quantity. For example, a temprature transducer will convert temperature to an equivalent electrical potential. This output signal can be used to control the physical quantity or display it.moreover this is of two type Digital or Analog electrical signals.
Q4. In charging by Induction
Answer : Option B
Explaination / Solution:
If a charged object placed near an uncharge object than redistribution of charge takes place in uncharge object and if we will earthed one surface of uncharged object than one charge goes to earth and other charge spread on its surface and it becomes charged.
Q5. Emission line spectrum of atoms contains
Answer : Option C
Explaination / Solution:
No Explaination.
Q6. The correct equation for a series LCR circuit excited by AC is
Answer : Option A
Explaination / Solution:
The LHS of equation contains expression for current through inductor, resistor and capacitor respectively. Each expression on LHS is a result of basic mathematical derivation. On the rhs we have the overall current in the circuit
Q7. Electric-field magnitude E at points inside and outside a positively charged spherical conductor having charge Q and a radius R are
Answer : Option B
Explaination / Solution:
Electric field inside a spherical conductor is zero since all the charge resides on the surface of the conductor and there is no charge in the interior of the conductor. For all external points, the conductor behaves as though its entire charge is concentrated at its center.
Q8. For small angles Snell’s law becomes
Answer : Option C
Explaination / Solution:
No Explaination.
Q9. A nucleus of mass number A has a radius R such that
Answer : Option D
Explaination / Solution:
A stable nucleus has approximately constant density. Packing protons and neutrons in the nucleus gives approximately the same total size result as packing hard spheres of a constant size (like marbles) into a tight spherical or almost spherical bag.
Q10. what is common to both biot savart law and ampere's law
Answer : Option D
Explaination / Solution:
Both Biot- Savart’s lawand ampere’s circuital lawdeal with the consequences of steady current. Ampere’s circuital law is to Biot- savart’s law as is Gauss’s law to Coulomb’s law in electrostatics.
