DC electric motors

Question 1

direction of force acting on two current-carrying conductors

Answer 1

current flow identical for both: attractive force
current flow opposite: repulsive force

Question 2

force (F) produced by an electric motor

Answer 2

= B i l
= 1/2 i^2 dL/dX

*current (i)
*length of wire (l)
*inductance in Henry’s (L)
*magnetic flux density (B)
*displacement (X)

Question 3

emf (e) produced by an electric motor

Answer 3

= B I v
= K ω (DC machines, linear motion)

*magnetic flux density (B)
*length (I)
*velocity (v)
*constant given to motor (K)
*rotational speed (ω)

Question 4

prediction of coil resistance (R) in an electric motor

Answer 4

= ρπDN / A

*resistivity (ρ)
*Diameter of coil spinning, not the wire (D)
*cross-sectional (A)
*number of turns (N)

Question 5

torque (T) of motor

Answer 5

= K φ I
= K I (DC machines, linear motion)

*constant given to motor (K)
*magnetic flux (φ)
*current (I)

Question 6

power (P) equation for a motor

Answer 6

VI = Tω + R I^2
input power = output power + losses

Question 7

losses in armature

Answer 7

= I^2 R

*current (I)
*resistance (R)