A cable consisting of a wire 3 mm in diameter and insulated with 3 mm thick dielectric of relative permittivity 4.5 is placed in water. Calculate the capacitance of 1 km length of the cable.

The inner and outer radii of a coaxial cable are 0.1 mm and 0.6 mm respectivley.If the core material has dielectric constant 12, calculate the capacitance per metre of the cable.

A lead pencil consists of cylinder of wood with a solid cylinder of graphite fitted into it. The diameter of the pencil is 7 mm. the diameter of the graphite is 1 mm and the length of the pencil is 10 cm. Calculate the weight of the whole pencil in grams correct to three places of decimals if the specific gravity of the the wood is 0.6 and of the graphite 2.3.

A lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in the interior. The diameter of the pencil is 7 mm and diameter of graphite is 1 mm. If the length of the pencil is 14 cm, find the volumes of the wood and that of the graphite.

The specific resistance ofo a wire 1.1 m long, 0.4 mm in diameter and haivng a total resistance of 4.2 ohm will be

A hollow copper tube of 5 m length has got external diameter equal to 10 cm and the walls are 5 mm thick . If specific resistance of copper is 1.7xx10^(-8) ohm meter. Calculate the resistance of the tube.

A glass (mu=1.5) convex lens of focl length 40 cm is placed in water (mu=1.3) .What will be its new focal length?

Resistance of a metal wire of length 2 m is 40 ohm. If the diameter of the wire is 0.3 mm. What will be the resistivity of the metal at that temperature?

In a parallel plate capacitor with air between the plates, each plate has an area of 6 xx 10^-3 m^2 and the distance between the plates is 3 mm. Calculate the capacitance of the capacitor. If this capacitor is connected to a 100 V supply, what is the charge on each plate of the capacitor?