My name is Martin Cole and i'm new to all this...

I've decided to start studying Electrical Engineering, and my topic touches on Series AC Circuits. I have been set some homework questions, and was needing a little help...

Any help will be appreciated... Its pretty hectic i think...

Martin

QUESTION 1

A coil with an unknown resistance and inductance is connected in series with a resistor of 15 Ω and a capacitor of 150,5 μF. The circuit is connected across a 240-V, 50-Hz supply. The power factor of the load is 0.7771 lagging. A voltage drop of 142,5 V is measured across the

resistor.

Calculate the voltage drops across the capacitor and the coil.

Calculate the resistance and inductance of the coil.

Calculate the power dissipated in the circuit.

Calculate the value of a capacitor to be connected in parallel with the

circuit to raise the overall power factor to 0,9563 lagging.

QUESTION 2

A voltage, represented by ν(t) = 339,411 sin (315t + (pi)/6 ) volt, supplies three parallel connected loads. The loads draw current from the supply as follow:

Load a : 17,2 A at a power factor of 0,5878 lagging

Load b : 9,5 A at unity power factor

Load c : 18,8 A at a power factor of 0,7071 lagging

Calculate the following:

The total current

The active and reactive components of the current

The value of the components in each load

The total impedance

The total active power dissipated in the circuit

The overall power factor of the circuit

The value of a capacitor to be connected in parallel to the circuit to cause

resonance to the parallel circuit

The total current and the overall power factor, should these loads be

connected in series

The value of a capacitor to be connected in series to the circuit to cause

resonance to the series circuit

QUESTION 3

A circuit consists of a coil in series with a 9,6Ω resistor. When a direct current of 6,5 A is passed through the coil, the voltage measured across the coil is 117V. With an alternating current of 6,5 A at 60 Hz, the voltage across the coil is 273 V. When the coil is connected to a 240 V/50 Hz supply, calculate the following and also draw the power triangle:

The voltage across the coil

The value of a capacitor to be connected in parallel with the coil to improve the power factor to 0,866 lagging