Question

The RC charging circuit in a camera flash unit has a voltage source of 305 V and a capacitance of 121 µF.

(a)Find its resistance *R* (in ohms) if the capacitor
charges to 90.0% of its final value in 12.2 s.

(b)Find the average current (in A) delivered to the flash bulb if the capacitor discharges 90.0% of its full charge in 1.04 ms.

Answer #1

**Given
RC circuit with voltage source V = 305 V**

**Resistor , R = ? ,
capacitor with capacitance C = 121*10^-6 F**

**Let the maximum charge of
the capacitor is, Q**

**we have the charging of a
capacitor relation is**

**q(t) =
Q(1-e^(-t/T))**

**a)**

**given t = 12.2
s**

**q(t)= 90*Q/100 =
0.9*Q**

**and T is time constant of RC
circuit, T = R*C**

**substituting the
values**

**0.9*Q =
Q(1-e^(-(12.2/(R*121*10^-6))))**

**solving for R, R = 43788.37
ohm**

**b) here we should calculate
the maximum charge on the capacitor from the relation
Q = C*V
Q = 121*10^-6*305 C**

** Q = 0.036905
C**

**now 90% of Q is , q =
Q*90/100 = 0.036905*90/100 C = 0.0332145 C**

**time duration is Dt =
1.04*10^-3 s
q = I*Dt**

**I =
q/Dt**

**I = 0.0332145/(1.04*10^-3)
A**

**I = 31.94 A
the average current is I = 31.94 A**

The RC charging circuit in a camera flash unit has a voltage
source 275 V and a capacitance of 125 F.
(a) Find its resistance R if the capacitor charges up to 90.0%
of it's final value in 15.0 s.
(b)Find the average current delivered to the flash bulb if the
capacitor discharges 90.0% of its full charge in 1.00 ms

28-2
Camera flash The camera flash is a capacitor that stores
a charge of 0.073 C at 330 V. The flash releases energy to a light
bulb with a resistance 5 Ω. This is an RC circuit, so the power
will decay. Find the:
a) capacitance of the flash in μF. Eq.
(26.15)
b) initial power in kW used by the light bulb. Eq.
(28.12)
c) decay time constant τ in ms. Eq. (28.30)

You are asked to design an RC circuit for a camera flash. You
want the flash to be ‘on’ for around the same time as the shutter
of the camera is open, which is about 60 ms. You are using a bulb
that will break if more than 0.5 A flow through it. For the flash
to be powered by 2 AA batteries (1.5 V each), what combination of
resistors and capacitors should you use? Assume the flash is an...

A camera flash gets its energy from a 150 μF capacitor and
requires 170 V to fire.
a) If the capacitor is charged by a 200 V source through an 18
kΩ resistor, how long must the photographer wait between flashes?
(Assume the capacitor is fully discharged with each flash.)
b) Of the total energy drawn from a battery in charging an RC
circuit, show that only half ends up as stored energy in the
capacitor. Hint: What happens to...

An RC circuit includes a 2-k Ω resistor, a battery with emf of
12.0 V and a capacitor. At t = 0 the switch is closed and the
charging of the capacitor begins. Knowing that the time constant of
the circuit is measured to be 1 ms calculate: (a) the capacitance
of the capacitor; (b) the time it takes for the voltage across the
resistor to reach 4 V, and (c) the charge accumulated on the
capacitor during this time...

In RLC series circuit, an AC source with a rms voltage of 220 V
and frequency 60 Hz is connected to a resistor, a capacitor 65 µF
and an inductor of inductance 185 mH. If the observed current is
4.4 A, evaluate the resistance of the resistor.

An AC voltage source, v(t)=220sin(314t) V, is applied to a
series RC circuit, with C = 100 *10^(-6)F, and R = (35) Ω.
a) Find the current, i (t).
b) Compute the power factor of the circuit.
c) Determine the average power consumed by the resistor.

A simple RC circuit has a resistance R = 1000 Ω and a
capacitance C = 3000 µF, the capacitor is flat.
a) Determine the time required for the capacitor to
charge up to 70% of the maximum charge.
b) Calculate the time necessary for the capacitor to
discharge up to 50% of its initial charge.

A 285-Ω resistor is in series with a 35.5 μF capacitor
and a 27.0-V voltage source with the circuit switch open and the
capacitor uncharged.
(a) What is the time constant of this RC circuit?
10.1175 ms
(b) Calculate the maximum charge the capacitor can
accumulate.
.000972 C
(c) Calculate the charge on the capacitor 5.25 ms after the switch
is closed.
.0005785083113C
Please check my answers.
Thanks!

A simple circuit can be created using a voltage source of some
form, let's say a battery, and a load, something that converts
electrical energy into some other form of energy. An example of a
load might be the thin wire filament in a light bulb, where the
electrical energy is being converted into thermal energy and light
energy. The resistance is a property of the load that determines
how much current flows through the load.
Ohm's Law relates the...

ADVERTISEMENT

Get Answers For Free

Most questions answered within 1 hours.

ADVERTISEMENT

asked 2 minutes ago

asked 5 minutes ago

asked 9 minutes ago

asked 21 minutes ago

asked 31 minutes ago

asked 37 minutes ago

asked 39 minutes ago

asked 43 minutes ago

asked 45 minutes ago

asked 47 minutes ago

asked 47 minutes ago

asked 56 minutes ago