Kiting during a storm. The legend that Benjamin Franklin flew a kite as a storm approached is only a legend — he was neither stupid nor suicidal. Suppose a kite string of radius 2.10 mm extends directly upward by 0.802 km and is coated with a 0.520 mm layer of water having resistivity 155 Ω·m. If the potential difference between the two ends of the string is 176 MV, what is the current through the water layer? The danger is not this current but the chance that the string draws a lightning strike, which can have a current as large as 500 000 A (way beyond just being lethal).

A potential difference of 3.00 µV is set up across a 2.00 cm length of a wire (with resistivity of 10-8 2'm) that has the cross-section area of 106 m². How much charge drifts through a cross section of the wire in 4.0 ms? Give your answer in µC.

A lightning rod on top of a building consists of an iron spike 1.5 m long with a circular crosssection of diameter 1.5 cm. During a lightning strike, the rod carries a current of 1000 A. What is the potential difference across the rod when this current flows? The resistivity of iron is 1.0 x 10-7 Ωm.

A wire 3.43 m long and 6.38 mm in diameter has a resistance of 11.6 mQ. A potential difference of 17.7 V is applied between the ends. (a) What is the current in amperes in the wire? (b) What is the magnitude of the current density? (c) Calculate the resistivity of the material of which the wire is made. (a) Number Units (b) Number i Units (c) Number i Units >

Electric current passing through a human body can be dangerous, even fatal, depending on the amount of current, the duration of the current, and the region of the body through which the current passes. However, currents less than about 0.5 mA are typically imperceptible. A current caused by a low potential difference typically travels through the outer layer of the skin. The resistance of the skin therefore determines how much current flows for a given potential difference. The resistance can be influenced by a number of factors, including whether the skin is wet or dry . For example, suppose an electric current of 89.0 µA follows a path through the thumb and index finger. When the skin is dry, the resistance along this path is 4.40 ✕ 105 Ω. What voltage (in V) is required for this current, in the case of dry skin? V When the skin is wet, the resistance is lowered to 1,950 Ω. What voltage (in V) is required for the same current, in the case of wet skin? V

Consider a steady beam of protons. Each proton has kinetic energy 20 MeV. The beam represents a current of 0.25 μA. a) What is the potential difference through which the protons are accelerated? b) If the beam is directed perpendicular to a flat surface, how many protons strike the surface in 3 seconds?

Wires A and B, having equal lengths of 41.8 m and equal diameters of 2.89 mm, are connected in series. A potential difference of 61.6 V is applied between the ends of the composite wire. The resistances are RA = 0.108 0 and Rg - 0.617 0. For wire A, what are (a) magnitude Jof the current density and (b) potential difference V? (c) Of what type material is wire A made (see the table below)? For wire B. what are (d) Jand (e) V? (f) Of what type material is B made? Resistivities of Some Materials at Room Temperature (20°C) Resistivity, p (N-m) Temperature Coefficient of Resistivity, a (K) Material Typical Metals 4.1 x 10- 1.62 x 10- 1.69 x 10- Silver 4.3 x 10- Copper Gold 4.0 x 10- 4.4 x 10- 0.002 x 10- 45 x 10- 6.5 x 10- 2.35 x 10 2.75 x 10- 4.82 x 10- 5.25 x 10- 9.68 x 10- 10.6 x 10- Aluminum Manganin Tungsten Iron Platinum 3.9 x 10- Typical Semiconductors 25 x 10 8,7 x 10- -70 x 10- Silicon, pure Silicon, n-type Silicon, p-type 2.8 x 10- Typical Insulators 10- 104 ~10M Glass Fused…