🏷️ LIMITED TIME OFFER: GET 20% OFF GRADE+ YEARLY SUBSCRIPTION →
Log in
Physics
1
answer
0
watching
76
views
20 Nov 2019

Consider an RL circuit, constitutedby the series ofa battery of voltage 12 V, a resistorof

R = 10, and an inductor of inductanceL.

(a) Draw the RL circuit;

(b) Describe qualitatively what happens tothecurrent i in the circuit after thebattery is

connected;

(c) Assume that the inductive time constantL=1second. Find the value of the currenti at

times t = 1 secondand t = 5 second.

Watch
1
answer
0
watching
76
views

For unlimited access to Homework Help, a Homework+ subscription is required.

Elin Hessel
Elin HesselLv2
9 Jul 2019

Unlock all answers

Get 1 free homework help answer.
Already have an account? Log in
Share

Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

Consider an L-R circuit as shown in the figure.Thebattery provides 12.0 V of voltage. The inductor hasinductanceL, and the resistor has resistanceR= 150 Ω. The switch is initiallyopen as shown. Attime t = 0, the switch is closed. At time t aftert = 0 the currentI(t) flows through the circuit as indicated in thefigure.
Part A:
What is the voltagechange Vr(t)across the resistor at time tafter t = 0?
a) RI(t)
b)-RI(t)
c) 12V
d)-12V
(correct answer b)
Part B:
What is the voltage changeVind(t)across the inductor at time t after t = 0? In thefollowingexpressions, ΔI/Δt denotes the time rate of change ofthecurrent in the inductor at time t?
a)RI(t)
b)-RI(t)
c)L(ΔI/Δt)
d)-L(ΔI/Δt)
e)12V
f)-12V
(correct answer d)
After the switch is closed, thecurrentin the circuit grows over time approaching a constant value.Ingeneral, at time t after a voltage source is connected to anL-Rcircuit, the current I(t) in the circuit is given bytheexpression
I(t)=V/R(1-e-t/τ)
where V is the voltage provided bythebattery, R is the resistance of the resistor, and τ is thetimeconstant characteristic of the circuit.
Part C:
What is the current I(τ) flowing inthecircuit shown in the figure at one time constant after t =0?
Express your answer in amperes.
Hint: To find the current inthecircuit after one time constant, use the expression forI(t)given in the problem, with t equal to τ. Do not try todeterminethe time constant for this circuit. You would not be ableto do sobecause the inductance L is unknown. Instead, afterplugging in thenumerical values for V and R appropriatefor this circuit andsubstituting τ for time, simplifyyour expression to get a numericalvalue for the current.

This set of problems is designed to help you prepare for the lab oncapacitors. Here are some things you should know.
The charge on a capacitor is proportional to the voltage. Theconstant of proportionality is the capacitance:
q=VC.
The simplest type of capacitor is a parallel plate capacitorconsisting of twoparallel conducting plates...DUH. If the plateseach have area A and
are separated by a distance d, the capacitance will be
C=Ke0A/d,
where e0 is the permittivity of free space (you measured that lastweek) and K is the dielectric constant of what ever material isbetween the plates. If the space between the plates is filled withvacuum, the dielectric constant is exactly 1. Air is pretty darnclose to 1.
When a capacitor is charged in a series circuit with a resistor,the charge builds up with time. Consider the circuit below.



When the switch, S, is thrown to position A, the battery, withvoltage V0, will supply a current through the resistor, R, thatcharges the capacitor C. The voltage across the capacitor at anygiven time is given by
V=V0(1-e-t/RC).
The product RC is known as the time constant. After waiting a timeequal to 1 time constant, the voltage on the capacitor is(1-e-1)=0.632 of V0. After 5RC the capacitor is nearly fullycharged and has a voltage of 0.993V0. Eventually, the voltagebuilds up to V0.
When the switch is thrown to position B, the capacitor willdischarge through the resistor. The voltage as a fuction of timewill be given by
V=V0(e-t/RC).
After a long enough time, the capacitor will fully discharge theresistor.

1. [1pt]
A parallel plate capacitor has plates with length and width of 5.7cm and are separated by 7.0 mm. The capacitance is measured to be1.479×10-11 F. What is the dielectric constant of the materialbetween the plates?

Correct, computer gets: 3.60

2. [1pt]
Consider a series circuit like the one shown above with a resistorof R=80. kilo-ohms and a capacitor of C=8.0 uF. What is the timeconstant of the circuit?

Correct, computer gets: 0.64 s


Hint: Don't forget to convert to Farads and ohms from uF andkilo-ohms.
3. [1pt]
If the battery has a voltage of 12 V, what is the voltage acrossthe capacitor after the switch has been in position A for 2 timeconstants?


Correct, computer gets: 10.38 V
4. [1pt]
What is the final charge on the capacitor after a long time?


Correct, computer gets: 9.60E-05 C
5. [1pt]
Now let's say that the capacitor has been fully charged and wethrow the switch to position B. How long will it take for thevoltage on the capacitor to be 0.891 V?


6. [1pt] What is the charge on the capacitor at this time?

Answer: ____________

Weekly leaderboard

Home
Homework Help 3,900,000
Physics 110,000
Start filling in the gaps now
Log in