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RL Lab

This lab report investigates the behavior of current passing through an inductor coil. When a step change is introduced to the applied voltage, the inductor opposes sudden changes in current, smoothing and slowing changes. When exposed to an AC applied voltage, the current amplitude increases as governed by an equation, with the current peaking lagging the voltage peak. Experimental values for resistance, inductance, and time constant are determined and found to be within the theoretical uncertainties.

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114 views3 pages

RL Lab

This lab report investigates the behavior of current passing through an inductor coil. When a step change is introduced to the applied voltage, the inductor opposes sudden changes in current, smoothing and slowing changes. When exposed to an AC applied voltage, the current amplitude increases as governed by an equation, with the current peaking lagging the voltage peak. Experimental values for resistance, inductance, and time constant are determined and found to be within the theoretical uncertainties.

Uploaded by

John Doe
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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RL CIRCUITS

INTRODUCTION:
In this lab report, we attempt to investigate the behaviour of current passing through a coil and the
changes observed in it, due to an abrupt change introduced in the applied voltage that exists across its
terminals. Furthermore, we analyze the AC behavior of the current as it passes through the coil so as to
observe its actions & applicability as a frequency filter
PROCEDURE:
I. STEP CHANGES:
While performing the experiment we see that the inductors, oppose the sudden changes in current and
hence end up smoothening and slowing down the changes in current observed brought about by changes
in circuit. Graphing our results as a Voltage v. Time & Current v. Time curve, we get the following:

Hence, the Equation 1 accurately describes the decay when the voltage is recorded and the curve plotted
by the equation fits the data almost perfectly.

The values recorded from our analysis are:


R s = 99.22 ± 0.3956 Ω R

L = 676.0 ± 8.384 mH
A0 = 3.393 ± 0.003844
From this we get the following results:
𝑅𝑅𝑇𝑇 = 𝑅𝑅𝐿𝐿 + 𝑅𝑅𝑆𝑆
= 133.7 ± 0.4677 + 99.22 ± 0.3956 Ω
= 232.92 Ω
676.0 × 10−3 𝐻𝐻
𝜏𝜏𝐿𝐿 = = 2.92 ∗ 10−3 𝑠𝑠
232.92 Ω

Theoretical value for the same is given by: 3.995 * 10-3 ± 1.393 * 10-4 s
Hence, we see that the recorded value is less than the theoretical value but loes within the range of
uncertainty. The difference can be accounted for due to error in recording as well as communication
between the devices.
II. RESPONSE TO AC APPLIED VOLTAGE:
Based on theory, we predict that the current going through the circuit will be much lower in this case and
the amplitude of current shall increase as governed by the equation:
𝜀𝜀𝑚𝑚 1
𝐼𝐼𝑚𝑚 = ∗� �
𝑅𝑅𝑇𝑇 �1 + 𝜔𝜔 2 𝜏𝜏 2
𝐿𝐿

The set-up of the circuit followed is given by:

The following values are observed through the course of the experiment:
V_pp Ch1
H_z V_pp Ch2 (V)
500 4.80 V 10.2 V
450 5.29 V 10.2 V
400 5.92 V 10.4 V
350 6.72 V 10.4 V
300 7.76 V 10.4 V
250 9.2 V 10.4 V
200 11.3 V 10.4 V
150 13.6 V 10.4 V
100 16.5 V 10.4 V
50 20.3 V 8.4 V

L = 683.3 mH
And we have the value of 𝜏𝜏𝐿𝐿 = 1.797 ∗ 10−3 ± 3.55 ∗ 10−0.05 𝑠𝑠
Plotting the values, we get the following curve:

On comparison we get that the value lies within the range of uncertainties of theoretical value, as well as
the fact that the current peak lags the voltage peak, as inferred from Ch1 leading Ch2.
UNCERTAINTIES:

∆𝜏𝜏 ∆𝐿𝐿 2 ∆𝑅𝑅𝑇𝑇 2


= �� � + � �
𝑇𝑇𝐿𝐿 𝐿𝐿 𝑅𝑅𝑇𝑇

∆𝑅𝑅𝑇𝑇 = �∆𝑅𝑅𝑆𝑆2 + ∆𝑅𝑅𝐿𝐿2

∆𝜏𝜏𝐿𝐿 = 1.546 × 10−4 𝑠𝑠


𝑅𝑅𝐿𝐿 = 133.7 ± 0.4674Ω
𝑅𝑅𝑆𝑆 = 99.22 ± 0.3956 Ω
𝐿𝐿 = 676.0 ± 3.384
𝜏𝜏𝐿𝐿 = 2.920 × 10−3

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