# DC Machine | My Assignment Tutor

Review QuestionsThe DC MachineQuestion 1A 1 m long copper wire carries a current of 10 A. This wire is exposed to a perpendicularbackground magnetic field of 0.5 T along its entire length. What is the force on the wire?Ans: 5 [N]Question 2The wire in Question 1 is moving with a velocity of 10 m/s. What is the back emf that isgenerated in this wire?Ans: 5 [V]Question 3A simple linear DC machine with a length of 0.5 m in a uniform magnetic field of 0.5 T andcircuit resistance of 2 Ω is supplied by a 24 V battery. How much current flows on start‐up ofthe motor the instant the switch is closed?Ans: 12 [A]Question 4What is the force on the wire in Question 3 on start‐up of the motor the instant the switch isclosed?Ans: 3 [N]Question 5In the absence of friction for the motor in Question 3, what would the terminal velocity ofthe wire be?Ans: 96 [m/s]Question 6If the static friction for the motor in Question 3 becomes 5 N, would the motor start?Ans: NoQuestion 7A load of 2 N is applied to the motor in Question 3 in the form of a fan. What is the terminalvelocity of the motor?Ans: 32 [m/s]Question 8A DC machine has 25 coils on the rotor, each coil has 60 turns per coil, what is the numberof conductors on the rotor?Ans: 3000 conductorsQuestion 9Find the total number of parallel paths for a simplex lap wound machine with 100 turns oneach of the 6 coils, with 2 poles?Ans: 2Question 10A 2 pole, 6 coil, 50 turn per coil, simplex lap wound DC generator is driven by a diesel motorat 1000 rpm. Find the peak voltage induced when the total flux per pole is 50 mWb.Ans: 500 [V]Question 11A 4 pole, 8 coil, 40 turn per coil, simplex wave wound permanent magnet machine isdrawing 5 A from a 100V DC supply and has reached steady state. If the flux density at thepole face is 1 T and the pole has an area of 100 cm2, find the torque induced, and the speedof the motor if the armature resistance total is 5 Ω? The equivalent electrical circuit of thismotor is shown below.Ans: 351.563 [RPM]Question 12A 2 pole, 6 coil, 20 turn per coil, simplex lap wound permanent magnet machine is suppliedfrom a 100V DC supply. The armature resistance total is 5 Ω. If the flux density at the poleface is 3 T and the pole has an area of 100 cm2, find the terminal velocity if frictional lossesin the machine are neglected? The equivalent electrical circuit of this motor is shown below.Ans: 833.3 [RPM]Question 13A 6 pole, 18 coil, 20 turn per coil, simplex wave wound machine is drawing 10 A from a 200Vsupply. If the flux density at the pole face is 3 T and the pole has an area of 100 cm2, findthe torque induced if the armature resistance total is 10 Ω?Ans: 103 [N.m]

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