Figure shows two identical triode tubes connected in paralle. The anodes are connected together, the grids are connected together and the cathodes are connected together. Show that the equivalent plate resistance is half of the individual plate resistance, the equivalent mutual conductance is double the individual mutual conductance and the equivalent amplification factor is the same as the individual amplification factor.
(##HCV_VOL2_C41_E01_049_Q01##)

The plate current, plate voltage and grid voltage of a 6F6 triode tube are related as i_p = 41 (V_p + 7 V_g)^(1.41) where V_p and V_g are in volts and i_p in microamperes. The tube is operated at V_p = 250 V, V_g = -20 V . Calculate (a) the tube current, (b) the plate resistance, (c) the mutual conductance and (d) the amplification factor.

Figure shows a metal rod PQ resting on the smooth rails AB and positioned between the poles of a permanent magnet. The rails, the rod and the magnetic field are in three mutually perpendicular directions. A galvonometer G connects the rails through a switch K. Length of rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = 9.0mOmega . Assume the field to be uniform. a. Suppose K is open and the rod is moved with a speed of 12cms^(-1) in the direction shown. Give the polarity and magnitude of the induced emf. b. Is there an excess charge built up at the ends of the rods when K is open? What if K is closed? c. With K open and the rod moving uniformly, there is no net force on the electrons in the rod PQ eventhough they do experience magnetic force due to the motion of the rod. Explain. d. What is the retarding force on the rod when K is closed? e. How much power is required (by an external agent) to keep the rod moving at the same speed (=12cms^(-1)) when K is closed? How much power is required when K is open? f. How much power is dissipated as heat in the closed circuit? What is the source of this power? g. What is the induced emf in the moving rod if the magnetic field is parallel to the rails instead of being perpendicular?