In the circuit below, the voltage source is a 5 V power supply. The inductor is
ID: 1393221 • Letter: I
Question
In the circuit below, the voltage source is a 5 V power supply. The inductor is considered to be ideal (it has no internal resistance) and large (say, 1 henry). R1=2 ? and R2=8 ?.
Units are required in all numerical answers.
Assume the switch had been closed for a long time. Use Kirchhoff's rules to determine the voltage drop across R2.
V2 =
At the instant just after the switch was opened, what is the current though the inductor?
IL =
At the instant just after the switch was opened, what is the current though R2?
I2 =
At the instant just after the switch was opened, what the current though R1?
I1 =
At the instant just after the switch was opened, what the magnitude of the voltage drop across R1?
V1 =
Suppose R1 were replaced with a 20 ? resistor and the switch had been closed for a long time. What would the magnitude of the voltage drop across R1 be just after the instant in which the switch was opened?
With R1 = 20 ?, V1 =
Explanation / Answer
Assume the switch had been closed for a long time. Use Kirchhoff's rules to determine the voltage drop across R2.
V2 = V as inductor will vehave as short cicuit after infinite time.
At the instant just after the switch was opened, current though the solenoid
IL = V/R2, as current can not change instantly
At the instant just after the switch was opened, the current though R2
I2 = V/R2, same as inductor
At the instant just after the switch was opened, the current though R1
I1 = V/R2, same as inductor as no other path.
At the instant just after the switch was opened, the magnitude of the voltage drop across R1
V1 = VR1
Suppose R1 were replaced with a resistor and the switch had been closed for a long time, the magnitude of the voltage drop across R1 be just after the instant in which the switch was opened
V1(20 M Omega) = same V as current is not changing