Solution:
Key concept: The phenomenon of electromagnetic induction is used in this problem. Whenever the number of magnetic lines of force (magnetic flux) passing through a circuit changes (or a moving conductor cuts the magnetic flux) an emf is produced in the circuit (or emf induces across the ends of the conductor) is called induced emf. The induced emf persists only as long as there is a change or cutting of flux.
When cylindrical bar magnet is rotated about its axis, no change in flux linked with the circuit takes place, consequently no emf induces and hence, no current flows through the ammeter A.
Hence the ammeter shows no deflection.
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According to corpuscular theory of light, the different colours of light are due to
|
(a) Different electromagnetic waves |
|
(b) Different force of attraction among the corpuscles |
|
(c) Different size of the corpuscles |
|
(d) None of the above |
When the momentum of a proton is changed by an amount P0, the corresponding change in the de-Broglie wavelength is found to be 0.25%. Then, the original momentum of the proton was
|
(a) p0 |
(b) 100 p0 |
(c) 400 p0 |
(d) 4 p0 |
An electron moving with the speed 5 
per sec is shooted parallel to the electric field of intensity 1 
. Field is responsible for the retardation of motion of electron. Now evaluate the distance travelled by the electron before coming to rest for an instant (mass of e = 9 
. charge = 1.6 
)
|
(a) 7 m |
(b) 0.7 mm |
(c) 7 cm |
(d) 0.7 cm |
Microscope is an optical instrument which
|
(a) Enlarges the object |
|
(b) Increases the visual angle formed by the object at the eye |
|
(c) Decreases the visual angle formed by the object at the eye |
|
(d) Brings the object nearer |
A element used for radioactive carbon dating for more than 5600 years is
|
(a) C - 14 |
(b) U - 234 |
(c) U - 238 |
(d) Po - 94 |
The material of wire of potentiometer is
|
(a) Copper |
(b) Steel |
(c) Manganin |
(d) Aluminium |