In the diagram is shown an RL circuit with a switch. ? = 95.0 V, R1 = 60.0 ?, R2
ID: 1493900 • Letter: I
Question
In the diagram is shown an RL circuit with a switch. ? = 95.0 V, R1 = 60.0 ?, R2 = 120.0 ? and L = 35.0 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
Current in inductor can not change instantly.
so just after closing switch, current in L will be zero.
hence i2 = 0 ........Ans
i1 = e/R1 = 95 / 60 = 1.58 A ......Ans
i = i1 + i2 = 1.58 A ......Ans
V_R2 = i2 R2 = 0 ......Ans
V_L = e = 95 Volt ....Ans ( Parallel branches have same PD )
-------------------
after long time.
constant current will flow through inductor and V_L = L di/dt = 0
and PD across R1 and R2 will be e. (parallel bracnhes)
i1 = 95 / 60 = 1.58 A ......Ans
i2 = 95/120 = 0.79 A ......Ans
i = i1 + i2 = 2.37 A .......Ans
V_R2 = e = 95 volt ......Ans
V_L = 0 .....Ans