A potentiometer has uniform potential gradient across it. Two cells connected in series (i) to support each other and (ii) to oppose each other are balanced over 6m and 2m respectively on the potentiometer wire. The e.m.f.’s of the cells are in the ratio of
|
(a) 1 : 2 |
(b) 1 : 1 |
(c) 3 : 1 |
(d) 2 : 1 |
(d) 2 : 1
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The phenomena involved in the reflection of radiowaves by ionosphere is similar to:
In the experiment of diffraction at a single slit, if the slit width is decreased, the width of the central maximum
|
(a) Increases in both Fresnel and Fraunhofer diffraction |
|
(b) Decreases both in Fresnal and Fraunhofer diffraction |
|
(c) Increases in Fresnel diffraction but decreases in Fraunhofer diffraction |
|
(d) Decreases in Fresnel diffraction but increases is Fraunofer diffraction. |
If a steady current of 4 amp maintained for 40 minutes, deposits 4.5 gm of zinc at the cathode and then the electro chemical equivalent will be
|
(a) 51 |
(b) 28 |
|
(c) 32 |
(d) 47 |
In a transformer, the coefficient of mutual inductance between the primary and the secondary coil is 0.2 henry. When the current changes by 5 ampere/second in the primary, the induced e.m.f. in the secondary will be
|
(a) 5 V |
(b) 1 V |
(c) 25 V |
(d) 10 V |
A double convex lens of glass of m = 1.5 has radius of curvature of each of its surface is 0.2 m. The power of the lens is
|
(a) + 10 dioptres |
(b) – 10 dioptres |
(c) – 5 dioptres |
(d) +5 dioptres |
The amplification factor of a triode valve is 15. If the grid voltage is changed by 0.3 volt the change in plate voltage in order to keep the plate current constant (in volt) is
|
(a) 0.02 |
(b) 0.002 |
(c) 4.5 |
(d) 5.0 |
