The circuit shown represents a simple strobe light whose flash frequency can be

Question

The circuit shown represents a simple strobe light whose flash frequency can be easily adjusted. The circuit consists of a battery (emf E=100V and internal resistance r=3ohms), a variable resistor R, a capacitor C=5microF, and a fluorescent lamp L.

There is a current through the lamp only when the potential across it reaches VL=90V, the breakdown voltage; then the capacitor discharges (instantaneously and completely) through the lamp causing it to flash. (The lamp has negligible capacitance and resistance).

(a) To what value should you tune R so that the lamp flashes 4 times per second? How important is the internal resistance of the battery?

(b) What you would the graph V(t), the voltage across the capacitor as a function of time, look like?

The circuit shown represents a simple strobe light whose ½flash frequency½ can be easily adjusted. The circuit consists of a battery (emf E=100V and internal resistance r=3ohms), a variable resistor R, a capacitor C=5microF, and a fluorescent lamp L. There is a current through the lamp only when the potential across it reaches VL=90V, the breakdown voltage; then the capacitor discharges (instantaneously and completely) through the lamp causing it to flash. (The lamp has negligible capacitance and resistance). (a) To what value should you tune R so that the lamp flashes 4 times per second? How important is the internal resistance of the battery? (b) What you would the graph V(t), the voltage across the capacitor as a function of time, look like?

Explanation / Answer

for an RC circuit, V = Vo*(1-e^(t/tau)) we have V = 90 at t= 0.25 s Vo = 100 tau = (R+r)*C solving we get, R = 21.7117 kohms

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.