In the diagram is shown an RL circuit with a switch. = 80.0 V, R1 = 75.0 , R2 =
ID: 1557910 • Letter: I
Question
In the diagram is shown an RL circuit with a switch. = 80.0 V, R1 = 75.0 , R2 = 150.0 and L = 60.0 H. Find the values of i1, the current through resistor R1 and i2, the current through resistor R2, the current through the switch, the potential difference across R2, the potential difference across L and the rate of change of the current di2/dt in the time just after the closing of the switch.
What is i1 just after the switch is closed?
What is i2 just after the switch is closed?
What is the value of the current in the switch just after the switch is closed?
What is the the potential difference across R2 just after the switch is closed?
What is the the potential difference across L just after the switch is closed?
What is i1 a long time after the switch is closed?
What is i2 a long time after the switch is closed?
What is the value of the current in the switch a long time after the switch is closed?
What is the the potential difference across R2 a long time after the switch is closed?
What is the the potential difference across L a long time after the switch is closed?
Explanation / Answer
When the switch is just closed there is no current through the inductor or R2 ,so the potential difference across the inductor must be 80 V.The potential difference across R1 is always 80 V when switch is closed ,regardless of the amount of time elapsed since closing.
a)
I1 =80/75 =1.0666 A
b)
I2 =0 A
c)
I=I1+I2 =1.0666 A
d)
E2=0 V
e)
E =80 V
After the switch has been close for long time the currents are stable and the inductor has no longer has an effect on the circuit.Then the circuit is simple two resistors in parallel network. ,each resistor has a potential difference of 80 V across it.
a)
I1 =80/75=1.0666 A
b)
I2 =80/150 =0.5333 A
c)
I =I1+I2 =1.5999 A
d)
E2=80 V
e)
L=0 H