CBSE 12TH PHYSICS - Online Test
Q1. According to Lenz’s law
Answer : Option B
Explaination / Solution:
Direction of an induced emf, or the current, in any circuit is such as to oppose the cause that produce it.
If the direction of the induced current were such as not to oppose then we would be obtaining electrical energy continuously without doing work, which is impossible
Q2. In various experiments on photo electricity the stopping potential for a given frequency of the incident radiation
Answer : Option B
Explaination / Solution:
The stopping potential is defined as the potential necessary to stop any electron even the electron with the most kinetic energy from reaching the other plate. By changing radiation intensity only no.of emitted electron changes their Kinetic energy will not change.
Q3. Digital weighing balance uses
Answer : Option D
Explaination / Solution:
A force transducer is also known as a force sensor this converts an input mechanical force into output electrical signal.Hence a force transducer is used in digital weighing balance.
Q4. Electrostatic force is
Answer : Option A
Explaination / Solution:
Electrostatics means charges at rest,or relatively at rest so this force can be applicable only when charge produce electric field which is constant which is possible only when charges at rest or relatively at rest.
Q6. If , , , and V represent the voltage across the inductor, resistor, capacitor and the source, respectively, on the phasor diagram
Answer : Option D
Explaination / Solution:
In Series LCR Circuit, current is same across all elements. Since for a resistor both current and voltage are in same phase, Vc is along the same direction as current in the phasor diagram.
In capacitor voltage lags current by 900 so it is at right angle with VR and in an inductor voltage leads current by 900 so it is at right angle with VR and directly opposite to Vc
Q7. Electric potential at a distance r from a point charges q is
Answer : Option D
Explaination / Solution:
Electric potential at a point V is the work done in bringing unit positive charge from infinity to the point in an electric field.
Q8. Total internal reflection can take place only if
Answer : Option C
Explaination / Solution:
No Explaination.
Q9. All nuclides with same mass number A are called
Answer : Option C
Explaination / Solution:
These are the elements having same atomic number but different mass number. They have the same atomic number because the number of protons inside their nuclei remains the same. The difference in their mass number is due to the difference in their number of neutrons.
Q10. cyclotron is used to
Answer : Option B
Explaination / Solution:
Cyclotron is a particle accelerator, which uses electric field to accelerate the charged particle and magnetic field to make it move in a circular path. During acceleration in the electric field, the particle acquires high energies of the order of a few million electron volts.
