# helping hand

Discussion in 'Homework Help' started by djstar, May 11, 2008.

1. ### djstar Thread Starter Active Member

Jan 26, 2008
37
0
could some one lease give me a helping hand with this please

17) A circuit consists of a 0.16μf capacitor connected across a 20V, 1 kHz supply. Also in parallel with the capacitor there is a 1kΩ resistor in series with a 0.18H coil.

Calculate

The current drawn from the supply
The phase angle of this current

(Use the j operator in your calculation.)

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
Calculate the impedance of the inductor and capacitor at 1KHz (source frequency) and then find the equivalent impedance of the circuit . Then divide the equivalent resistance of the circuit form the voltage to find the current.

3. ### djstar Thread Starter Active Member

Jan 26, 2008
37
0

X_(c ) = 1/2πfc = X_(c ) = 1/(2×π×1000×0.00000016) = 994.71 ohms

X_l=2πfl=2 × π ×1000 ×0.18 = 1130.97 ohms

1/(1/((1130.97+1000))+ 1/994.71) = 678 Ω

20/678 = 0.029 A

sorry about the poor formula but its was done in microsoft equation wizard and hasent came out that well on this site. im still stuck with part b and with what the j operator bit means.

4. ### djstar Thread Starter Active Member

Jan 26, 2008
37
0
just realised i used the wrong formula .its should be 0.02A with the formula

z= √(R^2+ (Xl-Xc )^2 )

5. ### Digi Dave Member

Apr 25, 2008
26
0
Z= 691.55678 ohms

I = 0.02892 amps

Phase angle 11'degrees leading because capacitor is taking more of the current than the inductor.
( tan of X / R . = 136.26/678 )

Last edited: May 11, 2008