- AThey do not last for long time.
- BThey are costly.
- CThey cannot be used with high voltage.
- DThey pollute the environment.
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$\mu<\mu',\text{M < M}'$
$\mu>\mu',\text{M < M}'$
$\mu<\mu',\text{M > M}'$
$\mu>\mu',\text{M > M}'$
Some magnetic flux is changed from a coil of resistance 10 ohm. As a result an induced current is developed in it, which varies with time as shown in figure. The magnitude of change in flux through the coil in webers is

|
(a) 2 |
(b) 4 |
(c) 6 |
(d) None of these |
The refractive index of a piece of transparent quartz is the greatest for
|
(a) Red light |
(b) Violet light |
(c) Green light |
(d) Yellow light |
If the speed of light were 2/3 of its present value, the energy released in a given atomic explosion will be decreased by a fraction
|
(a) 2/3 |
(b) 4/9 |
(c) 3/4 |
(d) 5/9 |
The respective radii of the two spheres of a spherical condenser are 12 cm and 9 cm. The dielectric constant of the medium between them is 6. The capacity of the condenser will be
|
(a) 240 pF |
(b) 240 μF |
(c) 240 F |
(d) None of the above |
If a radioactive substance reduces to
of its original mass in 40 days, what is its half-life
|
(a) 10 days |
(b) 20 days |
(c) 40 days |
(d) None of these |