Explanation:
The maximum energy that can be desirably stored in a capacitor is depends on the maximum electric field that the dielectric can withstand without breaking down. Therefore, capacitors of the same type have about the same maximum energy density, i.e. joules of energy per cubic meter.
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A microscope is focussed on a coin lying at the bottom of a beaker. The microscope is now raised up by 1 cm. To what depth should the water be poured into the beaker so that coin is again in focus ? (Refractive index of water is 
)
|
(a) 1 cm |
(b) |
(c) 3 cm |
(d) 4 cm |
Field at the centre of a circular coil of radius r, through which a current I flows is
|
(a) Directly proportional to r |
(b) Inversely proportional to I |
|
(c) Directly proportional to I |
(d) Directly proportional to |
A uniform wire of resistance 9 W is cut into 3 equal parts. They are connected in the form of equilateral triangle ABC. A cell of e.m.f. 2 V and negligible internal resistance is connected across B and C. Potential difference across AB is
|
(a) 1 V |
(b) 2 V |
(c) 3 V |
(d) 0.5 V |
Magnetic induction is a
|
(a) Scalar quantity |
(b) Vector quantity |
(c) Both (a) and (b) |
(d) None of the above |
The dispersive power of the material of lens of focal length 20 cm is 0.08. The longitudinal chromatic aberration of the lens is
|
(a) 0.08 cm |
(b) 0.08/20 cm |
(c) 1.6 cm |
(d) 0.16 cm |
The half-life of radioactive Polonium (Po) is 138.6 days. For ten lakh Polonium atoms, the number of disintegrations in 24 hours is
|
(a) 2000 |
(b) 3000 |
(c) 4000 |
(d) 5000 |
An electric lamp is marked 60 W, 230 V. The cost of 1 kilowatt hour of power is Rs. 1.25. The cost of using this lamp for 8 hours is
|
(a) Rs. 1.20 |
(b) Rs. 4.00
|
(c) Rs. 0.25 |
(d) Rs. 0.60 |
The field due to a magnet at a distance R from the centre of the magnet is proportional to
|
(a) |
(b) |
(c) |
(d) |
