# physics

posted by .

A source of e.m.f 110v and frequency 60hz is connected to a resistor, an indicator and a capacitor in series. When the current in the capacitor is 2A.the potential difference across the resistor is 80v and that across the inductor is 40v.calculate the -(1)potential difference across the capacitor (2)capacitance of the capacitor 3 inductance of the inductor

• physics -

The current is the same in all three since they are in series, 2 amps.

Say i = 2 cos w t
where w = 2 pi f = 120 pi

then
volts across resistor = iR = 2R cos wt
We measure 80 volts, no phase given so assume 2R=80 and R = 40

volts across inductor = Ldi/dt = -240piL sin wt
again no phase given so assume 240piL = 40 and L = .053 H

volts across capacitor = q/C = integral i dt /C = [1/(60piC)] sin wt

• physics -

Now we measure 110 volts across the whole circuit and that must be the sum of the three voltages.
Therefore
110 sin(wt+phi) = 80 cos wt - 40 sin wt + [1/(60 pi C)] sin wt

110 sin(wt+phi)= 80 cos wt + [-40+ 1/(60piC)]sin wt

110[sinwt cosphi + coswt sinphi] =80 cos wt + [-40+ 1/(60piC)]sin wt

sin wt terms:
110 cos phi = [-40+ 1/(60piC)]

cos wt terms:
110 sin phi = 80 solver for phi, then use in above to solve for C

## Similar Questions

1. ### Physics

1)A 15.0 resistor and a 20.0 resistor are connector in parallel. A 5.00 resistor is connected in series with this parallel arrangement. The resistors are connected across a 1.00(I think something else is suppose to be after that but …
2. ### Physics

A simple circuit is made of a power source, a rheostat and an ohmic resistor. The potential difference across the resistor is initially 5.0 +/- 0.1 V. A good lab student measures the current across the resistor to be 1.65 +/- 5 mA. …
3. ### College Physics

A simple circuit is made of a power source, a rheostat and an ohmic resistor. The potential difference across the resistor is initially 5.0 ± 0.1 V. A good lab student measures the current across the resistor to be 1.65 ± 5 mA. a)If …
4. ### Physics

A)Two identical resistors are connected in parallel across a 30-V battery, which supplies them with a total power of 7.0 W. While the battery is still connected, one of the resistors is heated so that its resistance doubles. The resistance …
5. ### Physics

A)Two identical resistors are connected in parallel across a 30-V battery, which supplies them with a total power of 7.0 W. While the battery is still connected, one of the resistors is heated so that its resistance doubles. The resistance …
6. ### Physics

In a series circuit, a generator (1400 Hz, 12.0 V) is connected to a 15.0- resistor, a 3.80-μF capacitor, and a 5.70-mH inductor. Find the voltages across (a) the resistor, (b) the capacitor, and (c) the inductor.
7. ### Physics

In a series circuit, a generator (1400 Hz, 12.0 V) is connected to a 15.0- resistor, a 3.80-ìF capacitor, and a 5.70-mH inductor. Find the voltages across (a) the resistor, (b) the capacitor, and (c) the inductor.
8. ### MONGU COLLEGE

A resistor of 15 ohms and an inductor of 4H and capacitor of 25 micro F are connected in series across 230V AC supply calculate. a.The frequency b.current c.voltage drop or pd across inductance.
9. ### College Physics

A circuit consists of 3 components connected between 2 terminals: A 6 V source, a 90 Ω resistor and a 0.01 F capacitor. The capacitor is initially uncharged. The voltage source is turned on. What is the voltage across the capacitor …
10. ### Physics

A 11.0-µF capacitor and a 50.0-µF capacitor are charged by being connected across separate 55.0-V batteries. (a) Determine the resulting charge on each capacitor. (b) The capacitors are then disconnected from their batteries and …

More Similar Questions