For a metallic wire, the ratio V/i (V = the applied potential difference, i = current flowing) is
|
(a) Independent of temperature |
|
(b) Increases as the temperature rises |
|
(c) Decreases as the temperature rises |
|
(d) Increases or decreases as temperature rises, depending upon the metal |
(b) Increases as the temperature rises
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$\text{Mr}^2$
$\frac{1}{2}\text{Mr}^2$
$\frac{1}4{}\text{Mr}^2$
$\frac{2}{5}\text{Mr}^2$
A signal emitted by an antenna from a certain point can be received at another point of the surface in the form of
|
(a) Sky wave |
(b) Ground wave |
(c) Sea wave |
(d) Both (a) and (b) |
A silver ball of radius 4.8 cm is suspended by a thread in the vacuum chamber. UV light of wavelength 200 nm is incident on the ball for some times during which a total energy of 1 × 10–7 J falls on the surface. Assuming on an average one out of 103 photons incident is able to eject electron. The potential on sphere will be
|
(a) 1 V |
(b) 2 V |
(c) 3 V |
(d) Zero |
A glass rod rubbed with silk is used to charge a gold leaf electroscope and the leaves are observed to diverge. The electroscope thus charged is exposed to X-rays for a short period. Then
|
(a) The divergence of leaves will not be affected |
|
(b) The leaves will diverge further |
|
(c) The leaves will collapse |
|
(d) The leaves will melt |
Electric charge is uniformly distributed along a long straight wire of radius 1mm. The charge per cm length of the wire is Q coulomb. Another cylindrical surface of radius 50 cm and length 1m symmetrically encloses the wire as shown in the figure. The total electric flux passing through the cylindrical surface is
|
(a) |
(b) |
(c) |
(d) |
A total charge Q is broken in two parts 
and 
and they are placed at a distance R from each other. The maximum force of repulsion between them will occur, when
|
(a) |
(b) |
|
(c) |
(d) |
When the speed of electrons increases, then the value of its specific charge
|
(a) Increases |
|
(b) Decreases |
|
(c) Remains unchanged |
|
(d) Increases upto some velocity and then begins to decrease |
The capacity of a parallel plate capacitor with no dielectric substance but with a separation of 0.4 cm is 2 μF. The separation is reduced to half and it is filled with a dielectric substance of value 2.8. The final capacity of the capacitor is
|
(a) 11.2 μF |
(b) 15.6 μF |
(c) 19.2 μF |
(d) 22. 4 μF |
