ELECTRIC OSCILLATIONS AND ELECTRIC WAVES. 273 



stream in ergs per second per square centimeter at a point distant 

 15 centimeters from the axis of the wire, (c) Find the intensity 

 of the electric field parallel to the wire in abvolts per centimeter. 

 (d) Find the intensity of the magnetic field in gausses at a point 

 distant 15 centimeters from the axis of the wire. Ans. (a) 

 1 8 X io 7 ergs per second; (b) 1.91 X io 6 ergs per square centi- 

 meter per second; (c) 6 X io 7 abvolts per centimeter; (d) 0.4 

 gauss. 



43. Consider two line wires in the form of two flat metal rib- 

 bons 50 centimeters wide and 3 centimeters apart. At a given 

 point p (see Fig. 43) the electromotive force between the 

 ribbons is 100 volts and the current in each ribbon is io amperes. 

 (a) Find the rate in ergs per second at which energy flows past 



generator J 3 cm* 



'10 amperes 

 ^100 volts receiver 



.10 amperes 



A' & 



Fig. 43. 



the point p from the generator towards the receiver using the 

 ordinary formula, P = El. (b) The electric field intensity 

 between the ribbons at the point p is 33.3 volts per centimeter 

 and the magnetic field between the ribbons is uniform and 

 perpendicular to the plane of the paper in Fig. 43. Find the 

 intensity of the magnetic field in gausses. Ans. (a) io 10 ergs 

 per second; (b) 0.251 gauss. 



Note. The energy which flows past the point p streams through the entire 

 region between the ribbons and therefore the sectional area of the energy stream is 

 150 square centimeters. Therefore the intensity of the energy stream (ergs per 

 square centimeter per second) can be calculated; and then knowing the electric 

 field intensity at p the intensity of the magnetic field can be calculated from equa- 

 tion (i) of Art. 134. 



