8/13/2019 Circuits 2 Lab 2

1/5

Ateneo de Naga UniversityCollege of Engineering

Experiment 2

A-C Power in a

Resistive Circuit

Date performed: November 19, 2013

Date submitted: November 26, 2013

Francisco, Sarah JoyLucio, Danilyn

Locsin, WilfredGO31

8/13/2019 Circuits 2 Lab 2

2/5

B. Objectives:

When an electric current flows through a resistive circuit element, some electric poweris dissipated. This is of course the case with a-c current as well as with d-c currents. In thisexperiment we shall examine the power relationships which arise when an a-c current flowsthrough a purely resistive circuit.

C. Theory

The Power formula indicates that P = IV, the only distinction with DC circuitsis that here it must be noted whereas this is a Peak value of power (if the current andvoltage are Peak values) or if it is an RMS value for power (in the case that bothcurrent and voltage are RMS values).

How are the RMS and Peak values of power related then? Well, since I rms =Ip/2 and V rms = Vp/2; and also since P rms = I rms V rms , then P rms = Ip/2 Vp/2= (IpVp)/2 = Pp/2.

Hence, the answer is that the RMS value of the power in an AC resistive circuitis one half its peak values. This is the only distinction worth noting between power inAC resistive circuits and in DC circuits.

D. Method of Experiment

1. Drawing of Experimental Setup

2. Outline of Procedurea. Connect the circuit shown in the Figure (see figure on the board).b. Using the VOM, adjust the voltage across the network to 20 volts rms.

Vs20 Vrms

0.998kHz

0

R1

220

R2470

8/13/2019 Circuits 2 Lab 2

3/5

8/13/2019 Circuits 2 Lab 2

4/5

f. Compute the percent difference of peak power

E. Equipment List

Oscilloscope VOM Variac Wattmeter 470-ohm resistor

220-ohm resistor

F. Data Section

TABLE 2

P-PVolts

(scope)

RmsVolts

(scope)

RmsCurrent(scope)

Ave.Power(scope)

Ave.Power

(wattmeter)

PeakPower(scope)

PeakPower

(wattmeter)

% DiffAve.

Power

% DiffPeak

Power220ohm

only

17.6 V 6.2225 28.28mA 175.95mW 1.9W 358.83mW

3.9W 90.74% 90.93%

470ohmonly

37.1V 13.1168 27.91mA 366.12mW 0.8W 722.11mW

2.1W 54.24% 65.61%

220+470

ohms

54.1 V 19.1273 27.72mA 530.19mW 0.9W 1.081W 1.8W 41.09% 39.94%

G. Sample Computations

Given:

RMS Voltage:

VRMS = ( )

220 ohm onlyP-P Volts (scope):

17.6 V

8/13/2019 Circuits 2 Lab 2

5/5

VRMS = ( )VRMS = 6.2225 V

RMS Current:

Average Power:

Peak Power:

% difference of two P ave values

% difference of two P peak values

( )