Posted by abdul rahman on .
Consider a circuit with an RL series with L=0.09 H and R=0.05 Ohm. At t=0 the circuit is connected to a battery which provides V0=12 V.
(a)How long does it take to the current to equal a fraction 0.95 of the steady state current?
(b) What is the energy stored (in Joules) in the magnetic field when the current equals a fraction 0.95 of the steady state current?
(c) What is the total energy delivered (in Joules) by the battery up to the time t found in part (a) ?
(d) How much energy (in Joules) has been dissipated in the resistor?

physics 
Henry,
I = E/R = 12/0.05 = 24q Amps = Steadystate current.
0.95I = 0.95 * 240 = 228A.
Vr + Vc = 12 Volts
228*00.05 + Vc = 12
Vc = 1211.4 = 0.6 Volts = Voltage across coil when i = 0.95I steadystate
a. Vc = 12/e^(t/T) = 0.6
e^(t/T) = 12/0.6 = 20
t/T = Ln20 = 3.0
T = L/R = 0.09/0.05 = 1.8 s.
t/1.8 = 3
t = 5.4 s.
c. Energy = E*I*t = 12*228*5.4=14,774.4
Joules.
d. Energy = I^2*R*t = (228)^2*0.05*5.4 =
14,036 Joules. 
physics 
abdul rahman,
Plz answer b part......(C) n (d) part are wrong !

physics 
Anonymous,
wrong answer

physics 
Anonymous,
please abdul answer of this question.

physics 
FLu,
All of the answers are wrong! Please help!

physics 
FLu,
sorry answer a) seems right the rest appears wrong though. Anyone for b),c),d)?

physics 
abdul rahman,
plz do u hav answers for other edx HW Q's ????

physics 
FLu,
Did you figure the above problem out Abdul?
Thank 
physics 
FLu,
I got d) 8165
you multiply 12/0.09
and than apply what Henry provided for answer c) 12*126*5.4=8165
It seems the numbers are getting mixed up, can someone figure out b) and c) with it?
thanks 
physics 
FLu,
I meant divide 12/0.09 and then multiply the result by 0.95 which is approx. 126
b) and c) anyone? 
physics 
FLu,
ANyone for Problem 2: Displacement Current a) please?
b) 0
Open Switch on an RL Circuit
b) and c) please? 
physics 
abdul rahman,
flu do u hav answers for Q2 part a
Q3 part b and part c, Q5 and Q7 all parts ??? 
physics 
My,
Anyone for this please?
Problem 2: Displacement Current a) please?
Problem: Open Switch on an RL Circuit
b) and c) please? 
physics 
Ira,
Yes, please the question below too?!
Problem 2: Displacement Current a)
Problem: Open Switch on an RL Circuit
b) and c) 
physics 
Ju,
Please help!

physics 
FLu,
Can somebody help with Problem: Displacement Current please?
I thought the formula is:
(1.25663706*10^6*0.04*0.2*0.0705)/(2*pi*0.05^2)
However, I am not getting the correctr answer. 
physics 
dd,
i need only the c1

physics 
ev,
C2: integral 1 to 5.4 of (12/0.05)^2)* (1e^((0.05 t)/0.09))^2 * 0.05 dt
C1: B + C2 
physics 
Supraconductor,
remember that E=1/2.L.I² for b)

physics 
Ur,
Anybody figure out c)?

physics 
FLu,
Anyone for Problem
Opening a Switch on an RL Circuit
c) please? 
physics 
Supraconductor,
Flu > ev give you the answer d (just integrate what he wrote)
now you have d) you have just to do answer c) = b) + d)