Answer the following: (a) The top of the atmosphere is at about 400 kV with respect to the surface of the earth, corresponding to an electric field that decreases with altitude. Near the surface of the earth, the field is about  100Vm-1 . Why then do we not get an electric shock as we step out of our house into the open? (Assume the house to be a steel cage so there is no field inside!)

Answer the following: (a) The top of the atmosphere is at about 400 kV with respect to the surface of the earth, corresponding to an electric field that decreases with altitude. Near the surface of the earth, the field is about  100Vm-1 Read More …

A small sphere of radius 1r and charge q1 is enclosed by a spherical shell of radius r2 and charge . q2 Show that if q1 is positive, charge will necessarily flow from the sphere to the shell (when the two are connected by a wire) no matter what the charge  q2 on the shell is

A small sphere of radius 1r and charge q1 is enclosed by a spherical shell of radius r2 and charge . q2 Show that if q1 is positive, charge will necessarily flow from the sphere to the shell (when the two are Read More …

In a Van de Graaff type generator a spherical metal shell is to be a 15×106 V electrode. The dielectric strength of the gas surrounding the electrode is 5×107 Vm-1 . What is the minimum radius of the spherical shell required? (You will learn from this exercise why one cannot build an electrostatic generator using a very small shell which requires a small charge to acquire a high potential.)

In a Van de Graaff type generator a spherical metal shell is to be a 15×106 V electrode. The dielectric strength of the gas surrounding the electrode is 5×107 Vm-1 . What is the minimum radius of the spherical shell required? (You Read More …

A parallel plate capacitor is to be designed with a voltage rating 1 kV, using a material of dielectric constant 3 and dielectric strength about   107 Vm-1 . (Dielectric strength is the maximum electric filed a material can tolerate without breakdown, i.e., without starting to conduct electricity through partial ionization.) For safety, we should like the field never to exceed, say 10% of the dielectric strength. What minimum area of the plates is required to have a capacitance of 50 pF?

A parallel plate capacitor is to be designed with a voltage rating 1 kV, using a material of dielectric constant 3 and dielectric strength about   107 Vm-1 . (Dielectric strength is the maximum electric filed a material can tolerate without breakdown, i.e., without Read More …

A cylindrical capacitor has two co-axial cylinders of length 15 cm and radii 1.5 cm and 1.4 cm. The outer cylinder is earthed and the inner cylinder is given a charge of 3.5 μC . Determine the capacitance of the system and the potential of the inner cylinder. Neglect end effects (i.e., bending of field lines at the ends).

A cylindrical capacitor has two co-axial cylinders of length 15 cm and radii 1.5 cm and 1.4 cm. The outer cylinder is earthed and the inner cylinder is given a charge of 3.5 μC . Determine the capacitance of the system and Read More …

Answer carefully: (a) Two large conducting spheres carrying charges Q1 and Q2 are brought close to each other. Is the magnitude of electrostatic force between them exactly given by Q1  Q2    /4πε0 r2, where r is the  distance between their centres? (b) If Coulomb’s law involved 3 1/ r dependence (instead of  1/ r2 ), would Gauss’s law be still true?

Answer carefully: (a) Two large conducting spheres carrying charges Q1 and Q2 are brought close to each other. Is the magnitude of electrostatic force between them exactly given by Q1  Q2    /4πε0 r2, where r is the  distance between their centres? (b) If Coulomb’s Read More …

A spherical capacitor has an inner sphere of radius 12 cm and an outer sphere of radius 13 cm. The outer sphere is earthed and the inner sphere is given a charge of 2.5 μC . The space between the concentric spheres is filled with a liquid of dielectric constant 32. (a) Determine the capacitance of the capacitor. (b) What is the potential of the inner sphere? (c) Compare the capacitance of this capacitor with that of an isolated sphere of radius 12 cm. Explain why the latter is much smaller.

A spherical capacitor has an inner sphere of radius 12 cm and an outer sphere of radius 13 cm. The outer sphere is earthed and the inner sphere is given a charge of 2.5 μC . The space between the concentric spheres Read More …

Show that the force on each plate of a parallel plate capacitor has a magnitude equal to (1/2)QE where Q is the charge on the capacitor, and E is the magnitude of electric field between the plates. Explain the origin of the factor 1/2

Show that the force on each plate of a parallel plate capacitor has a magnitude equal to (1/2)QE where Q is the charge on the capacitor, and E is the magnitude of electric field between the plates. Explain the origin of the factor Read More …

A 4 μF capacitor is charged by a 200 V supply. It is then disconnected from the supply, and is connected to another uncharged 2 μF capacitor. How much electrostatic energy of the first capacitor is lost in the form of heat and electromagnetic radiation?

A 4 μF capacitor is charged by a 200 V supply. It is then disconnected from the supply, and is connected to another uncharged 2 μF capacitor. How much electrostatic energy of the first capacitor is lost in the form of heat Read More …

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