CBSE 12TH PHYSICS - Online Test
Q1. Stopping potential in the experimental set up shown in figure is
Answer : Option A
Explaination / Solution:
The negative potential of the plate at which the photo electric current becomes zero is called stopping potential or cut-off potential. Its value is negative because some electron reach to the plate with their kinetic energy at zero potential.
Q2. Which of these can be used to convert position signals to electrical signals?
Answer : Option B
Explaination / Solution:
Potentiometer is device which can be used to measure and control frequency,temprature etc.Hence changing frequency in signal coverts it into electrical signal.
Q3. Charge is quantized means
Answer : Option B
Explaination / Solution:
Total charge transferred from one body to other can be calculated by the number of electrons it is known as quantisation of charge given by q=±ne, where n= number of electrons , which should be an integer.
Q4. In Geiger-Marsden experiment, actual results was
Answer : Option D
Explaination / Solution:
No Explaination.
Q5. Average power supplied to an inductor over one complete cycle
Answer : Option B
Explaination / Solution:
In the first half of the cycle, power is supplied to the inductive circuit. In the next half the inductor dissipates the energy supplied by circuit.
Thus overall no power is supplied to the circuit
Q6. Electric Potential is
Answer : Option C
Explaination / Solution:
Electric potential V is the work done in bringing unit positive charge from infinity to the point in an electric field, and the potential energy is the work done in bringing any finite charge from infinity to the point in an electric field. They are related as,
Q7. For a rectangular slab, refraction takes place at
Answer : Option D
Explaination / Solution:
No Explaination.
Q8. The nuclei of isotopes of a given element contain the same number of
Answer : Option A
Explaination / Solution:
Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of a given element have the same number of protons in each atom.
Q9. The magnitude of the magnetic field due to a circular coil of radius R carrying a current I at an axial distance x from the centre is
Answer : Option B
Explaination / Solution:
magnetic field at a point located at a distance x from the center of the coil of radius R carrying current along its axis is
Q10. Two resistances are connected in the two gaps of a meter bridge. The balance points is 20 cm from the zero end. When a resistance of 15 ohm is connected in series with the smaller of the two resistances, the null point shifts to 40 cm. The smaller of the two resistances has the value (in ohm)
Answer : Option A
Explaination / Solution:
Let the resistances be P and Q. When balanced,
