1. Consider a permanent-magnet dc motor with the following parameters:
Rₐ = 0.35 Ohm, Lₐ = 1.5 mH, kₑ = 0.5 V/rad/s, kₜ = 0.5 Nm/A, and Jₘ = 0.02 kg m². The rated torque of this motor is 4 Nm.
Plot the steady-state torque-speed characteristics for V = 100 V, 60 V, and 30 V.

2. The motor above is driving a load whose torque requirement remains constant at 3 Nm, independent of speed. Calculate the armature voltage Vs to be applied in steady-state if this load is to be driven at 1,500 rpm.

For the closed feedwater heater below, feedwater enters state 3 at a pressure of 2000 psia and temperature of 420 °f at a rate of ix10 ibhr. the feedwat extracted steam enters state 1 at a pressure of 1000 psia and enthalpy of 1500 btu/lbm. the extracted er leaves at an enthalpy of 528.7 btu/lbm steam leaves as a saturated liquid. (16) a) determine the mass flow rate of the extraction steam used to heat the feedwater (10) b) determine the terminal temperature difference of the closed feedwater heater

Thermal stresses are developed in a metal when its a) initial temperature is changed b) final temperature is changed c) density is changed d) thermal deformation is prevented e) expansion is prevented f) contraction is prevented

The thermal expansion or contraction of a given metal is a function of the f a)-density b)-initial temperature c)- temperature difference d)- linear coefficient of thermal expansion e)- final temperature f)- original length