An ion source is producing 6li ions, which have charge +e and mass 9.99 × 10-27 kg. the ions are accelerated by a potential difference of 13 kv and pass horizontally into a region in which there is a uniform vertical magnetic field of magnitude b = 1.0 t. calculate the strength of the smallest electric field, to be set up over the same region, that will allow the 6li ions to pass through undeflected.

Athin electrical heater is inserted between a long circular rod and a concentric tube with inner and outer radii of 20 and 40 mm. the rod (a) has a thermal conductivity of ka = 0.15 w/(m*k), while the tube (b) has a thermal conductivity of kb = 0.8 w/(m*k) and its outer surface is subjected to convection with a fluid of temperature t= -15°c and heat transfer coefficient 60 w/(m2 *k). the thermal contact resistance between the cylinder surfaces and the heater is negligible. (a) determine the electrical power per unit length of the cylinders (w/m) that is required to maintain the outer surface of cylinder b at 15°c. (b) what is the temperature at the center of cylinder a?