Answer and Explanation:
The DC motor has coils inside it which produces magnetic field inside the coil and due to thus magnetic field an emf is induced ,this induced emf is known as back emf. The back emf always acts against the applied voltage. It is represented by 
The back emf of the DC motor is given by 
Here N is speed of the motor ,P signifies the number of poles ,Z signifies the the total number of conductor and A is number of parallel paths
As from the relation we can see that back emf and speed ar dependent on each other it means back emf limits the speed of DC motor
Answer:
51.4 Ohms
Explanation:
By applying voltage division rule
where v is voltage, subscripts i and f represnt initial and final, R is resistance, m is internal and l is external.Substituting 7V for final voltage, 10V for initial voltage and the external resistance as 120 Ohms then
Answer:0.2A
Explanation:
First, write KCL
i1-i2-i3=0
Then, replace currents with viltages and resistors.
V2-10v/100-v2/200-v2/400=0
V2-40=0
V2=40v
I hope it was helpful
Given:
diameter of sphere, d = 6 inches
radius of sphere, r = 
= 3 inches
density, 
= 493 lbm/ 
S.G = 1.0027
g = 9.8 m/ 
= 386.22 inch/ 
Solution:
Using the formula for terminal velocity,
= 
(1)
where,
V = volume of sphere
= drag coefficient
Now,
Surface area of sphere, A = 
Volume of sphere, V = 
Using the above formulae in eqn (1):
= 
= 
= 
Therefore, terminal velcity is given by:
= 
inch/sec
