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3 years ago

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A charging RC circuit controls the intermittent windshield wipers in a car. The emf is 12.0 V. The wipers are triggered when the

voltage across the 125 mu or micro F capacitor reaches 10.0 V; then the capacitor is quickly discharged (through a much smaller resistor) and the cycle repeats. What resistance should be used in the charging circuit if the wipers are to operate once every 1.80 s?

1 answer:

lilavasa [31]3 years ago

3 0

Answer:

$R=803k\Omega$

Explanation:

We have the following information,

$V_0 = 12V\\V=10V\\c= 1.25*10^{-6}F\\t=1.8s$

We apply the equation for capacitor charging the voltage across it,

$V=V_0 (1-e^{-t/x})\\e^{-t/x}=1-(\frac{V}{V_0})\\-\frac{t}{Rc}=ln(\frac{V}{V_0})\\R=-\frac{t}{ln(\frac{V}{V_0})*c}$

Replacing values,

$R=-\frac{1.8}{ln(10/12)*1.25*10^{-6}}$

$R=803k\Omega$

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Here θ = 23 for first polariser

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For second polariser θ = 90 - 23 = 67 degree

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Answer:

Angle of refraction for red light is $43.01^{\circ}$

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Explanation:

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According to law of refraction $\mu =\frac{sini}{sinr}$

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Therefore angle of refraction for red light is $43.01^{\circ}$

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Re-arranging the equation,

$\frac{v}{r}=\frac{qB}{m}$ (1)

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Substituting into (1),

$\frac{2\pi}{T}=\frac{qB}{m}$

We also know that 1/T is equal to the frequency f, so

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