# RLC CCT help

1. Aug 5, 2017

### Elliot_Bennett

How can taking voltage and current readings from an AC supplied CCT with either a resistive, capacitive or inductive load (gradually increasing the load for each) show the difference in phase angle between voltage and current for each component? Many thaks for any help.

2. Aug 5, 2017

### cnh1995

Welcome to PF!
Could you elaborate?

3. Aug 5, 2017

### Elliot_Bennett

I recently did an experiment whereby an AC generator supplied a capacitive, resistive or inductive load, for each readings of voltage and current were taken from the AC Generator showing how it reacted to various levels of RLC load. On a capacitive load as the load value was increased the current and voltage both increased, on an Inductive load as the load was increased the voltage rose and current fell and on a Resistive load as the load was increased voltage rose and current dropped (but showed less change than a purely inductive load).

4. Aug 5, 2017

### cnh1995

So did you use a series RLC circuit and changed the componemt values one at a time or did you use purely resistive and purely reactive circuits?
What do you mean by 'load' here? Did you increase the capacitance?

5. Aug 5, 2017

### Elliot_Bennett

No we did not use a series RLC circuit. Purely resistive, purely capacitive and purely inductive circuits with only the relevant component in each circuit, for each the value of the inductor, capacitor or resistor was increased. I.E for resistive from 50-450 ohms at 50 ohm intervals.

6. Aug 5, 2017

### cnh1995

If the ac voltage source were ideal, there would be no change in voltage with the change in load. The voltage is changing because of the internal impedance of the source.
When you increase the resistance and inductance, you are decreasing the load. Here, the current drops and hence, the voltage across the internal impedance also drops, which gives more voltage across the resistance or inductance.
In case of purely capacitive circuit, increasing the capacitance means increasing the load. Here, the current is expected to increase, but since the voltage is also increasing, it is something like the 'Ferranti effect'.

7. Aug 5, 2017

### cnh1995

In #3, you only described the magnitude changes of voltage and current while in #1, you were asking about their phase difference. What is your question about the phase difference?

8. Aug 5, 2017

### jim hardy

Can we assume that generator has a voltage regulator ?

To understand what's going on you need to lock the excitation,, ie switch the voltage regulator from "Auto" to "Manual". Otherwise you're just testing the voltage regulator.