# Calculating the average power supplied by a source

• TheBigDig
In summary, the circuit has an impedance of 8-12.5j Ω and a capacitive reactance of -12.5j S. The current through the circuit is calculated using the Y = 1/Z = I/V relation, yielding an output of 0.5A. Thanks so much. Got the answer in the end. You were a terrific aid.
TheBigDig
1. For the circuit shown in (Figure 1) , where V= 2.8 cos(2 t+ 0.3 ) , R= 8 Ω and C= 4×10−2 F , find the average power supplied by the source, Ps and the average power absorbed by the resistor PR .2. p (t) = v(t)i(t) = VmIm cos (ωt + θv) cos (ωt + θi)
PR = (1/2)(V2m/R)3. From the expression given, I've managed to isolate the value of omega and Vm. But I'm confused as to how to find the power if we're not given an expression for the current.

You're supposed to derive one from your knowledge of ##V_m## and the circuit.

TheBigDig said:
1. For the circuit shown in (Figure 1) , where V= 2.8 cos(2 t+ 0.3 ) , R= 8 Ω and C= 4×10−2 F , find the average power supplied by the source, Ps and the average power absorbed by the resistor PR .2. p (t) = v(t)i(t) = VmIm cos (ωt + θv) cos (ωt + θi)
PR = (1/2)(V2m/R)3. From the expression given, I've managed to isolate the value of omega and Vm. But I'm confused as to how to find the power if we're not given an expression for the current.

I think you are complicating the problem. This is a series RC circuit excited with an ac source. You know the resistance and capacitance. What is the capacitive reactance? What is the total impedance of the circuit?

cnh1995 said:
I think you are complicating the problem. This is a series RC circuit excited with an ac source. You know the resistance and capacitance. What is the capacitive reactance? What is the total impedance of the circuit?
So I found the reactance to be equal to -12.5j S and the total impedance to be 8-12.5j Ω. Am I right in saying that I can then use the Y = 1/Z = I/V relation to find the current?

TheBigDig said:
So I found the reactance to be equal to -12.5j S and the total impedance to be 8-12.5j Ω
Yes.
TheBigDig said:
Am I right in saying that I can then use the Y = 1/Z = I/V relation to find the current?
Yes. You can also use the magnitude of impedance and voltage to calculate the magnitude of current, and then calculate the power consumed by the resistor.

cnh1995 said:
Yes.

Yes. You can also use the magnitude of impedance and voltage to calculate the magnitude of current, and then calculate the power consumed by the resistor.

cnh1995 said:
Yes.

Yes. You can also use the magnitude of impedance and voltage to calculate the magnitude of current, and then calculate the power consumed by the resistor.
Thanks so much. Got the answer in the end. You were a terrific aid.

cnh1995

## What is the formula for calculating average power?

The formula for calculating average power supplied by a source is: average power = (energy transferred/ time taken).

## What units are used for average power?

The units for average power are watts (W). This is because power is a measure of the rate at which energy is transferred.

## How is average power different from instantaneous power?

Average power is the average rate at which energy is transferred over a given period of time. Instantaneous power, on the other hand, is the power at a specific moment in time. Average power takes into account the fluctuations of power over time, while instantaneous power only reflects the power at a specific instant.

## Can average power be negative?

Yes, average power can be negative. This occurs when the source is supplying energy in one direction, and then absorbing energy in the opposite direction. In this case, the average power will be negative, indicating that the source is supplying less energy than it is absorbing over a given period of time.

## How can I measure the average power supplied by a source?

Average power can be measured using a power meter, which measures the rate of energy transfer over a specific period of time. This measurement can then be used to calculate the average power supplied by the source. Another method is to measure the voltage and current at the source and use the formula for average power to calculate the value.

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