A 40-mH ideal inductor is connected in series with a 50 Ω resistor through an ideal 15-V DC power supply and an open switch. If the switch is closed at time t = 0 s, what is the current 7.0 ms later? O 650 mA O 850 mA O 300 mA O 280 mA O 550 mA

Respuesta :

Answer:i=300 mA

Explanation:

Given

inductance(L)=40 mH

Resistor(R)=[tex]50 \Omega [/tex]

Voltage(V)=15 V

Time constant([tex]\tau [/tex])=[tex]\frac{L}{R}[/tex]

[tex]\tau =\frac{40\times 10^{-3}}{50}=8\times 10^{-4}[/tex]

current [tex]i_0=\frac{V}{R}[/tex]

[tex]i_0=\frac{15}{50}=0.3 A[/tex]

Current as a function of time is given by

[tex]i=i_0\left ( 1-e^{-\frac{t}{\tau }}\right )[/tex]

[tex]i=0.3\times 0.9998[/tex]

i= 299.95 mA