Physic of light bulb

DC Circuits: Electric Power

PHY 114 Lab Report

10/09/2013

Abstract:
The purpose of this experiment was to look at electric power dissipated in a load resistor in a circuit with a real power source, which has a finite internal resistance. We discover a surprising result about how to deliver the most power to a device from a source. Consider a simple circuit in which a battery of voltage drives a current through a resistor of resistance. As we have seen, the battery is continuously doing work by raising the potentials of charges, which flow into its negative terminal and then flow out of its positive terminal. We will also see that power you can extract from a real source is maximized for a particular value of load resistor. Consider a (positive) charge, which flows through the battery from the negative terminal to the positive terminal. The battery raises the potential of the charge by, so the work the battery does on the charge is. The total amount of charge, which flows through the battery per unit time, is, by definition, equal to the current flowing through the battery. Thus, the amount of work the battery does per unit time is simply the product of the work done per unit charge, and the charge passing through the battery per unit time, In other words, a mechanical analog is matching a propeller load resistor.
Objective:
The objective of this lab was to experimentally determine the load resistance (RL) value at which the power is optimized in a DC circuit.

Procedure:
We have to measure the R0 directly using the DMM on ohms ranges, the effective internal resistor must be removed from the circuit, 9.98 v 0.087 A.
And then we had connect the circuit, TA helped us and explained us how to connect the circuit we a real power source with voltage V0 and internal resistance R0, the actual power supply has a very low internal resistance so we add R0 externally but consider the combination as the black box. This combined element, supply + R0 is connected to a load resistor RL the meters.
After connecting the DC circuit we had to measure (I,V) as we step through values of RL. We had to measure in increments of 10 ohms for the range of 10-100 ohms, we measure in increments of 20 ohms for 120-200 ohms range, and we had to measure in increments of 100 ohms for the 300-1000 ohms range.
We had to change to 200 and redo the process as we did in the past tries. step by step.
After finishing we have to calculate the power P=I.V dissipated in the resistor for each measurement and male a plot of power P vs RL. From this plot eyeball the load resistance, which maximizes the power output.

DATA:
Pl = (lo/ Ro Rl MY)^2 . Rl mx
Pl= Vo^2/ (Ro + Rmx)
= Pl max / p gen . 100
100 = Pl mx = (10v/117.9 + 100)^2 .120= 0.248
200= Pl mx =(10v/400)^2 .200= 0.125
100= P gen =100/100+120=0.455
200=P gen =100/200+200=0.25
Error percent:
(0.248/0.455) *100% = 54.5%
Results:
Ro = 100 ohms
V=x (A/(B+X)) ^ 2
A: 10.11 +/- 0.04021
B: 117.9 +/- 0.8966
RMSE: 0.002258

R0= 200 ohms
V=x(A/(B+X)) ^2
A: -10.05 +/- 0.05228
B: 201.9 +/- 1.869
RMSE: 0.001688

Discussion:
To begin, we first find the measure Ro directly using the DMM on ohms range.
Conclusion:
The objective of this experiment was to measure the voltage across the material and investigate resistance and temperature of the conductor. This lab experiment was accomplished after we successfully gathered the results. The results which the graph showed that the voltage and the resistance were change and transferred the heat and the tempt.