Circuit Report

Only available on StudyMode
  • Download(s): 43
  • Published: March 30, 2006
Read full document
Text Preview
Objective

The aim of the experiment is to understand the properties of the passive elements and the resonance.

Apparatus

1. Unknown Box

2. Passive Elements: Resistors, Inductors and Capacitors

3. A.C. Power supply

4. Connecting Wires

5. Multimeter

Introductory Theory

Passive elements

Passive elements are elements that can either absorb energy or store energy.

There are 3 types of passive elements, which are shown below:

Resistor: A resistor is a two-terminal electrical or electronic component that resists an electric current by producing a voltage drop between its terminals in accordance with Ohm's law.

Inductor: An inductor is a passive electrical device employed in electrical circuits for its property of inductance. It stores energy in magnetic form.

Capacitor: A capacitor is a device that stores energy in the electric field created between a pair of conductors on which equal but opposite electric charges have been placed.

Black

It is a box which contains an unknown passive element other than a resistor. Both of them are connected in series.

Resonance

A circuit is said to be in resonance when its impedance is equal to its resistance. There are two types of resonant circuit: Series and Parallel.

2 types of resonant circuits are shown as the following:

Series Resonant Circuit: Passive elements are connected in series.

Parallel Resonant Circuit: Passive elements are connected in parallel.

.

Experiment 1: Unknown Component

Aim

The blackcontains an unknown passive element other than a resistor and it is connected to a resistor in series. The objective is to find the unknown component in the black box.

Procedure:

1) The unknown box is connected in series with a resistor, R in the circuit.

2) An AC power supply is connected to the circuit.

3) The potential different is set to be 1V throughout the experiment.

4) A multimeter is connected across the unknown box to measure its potential difference, VZ.

5) The results are recorded in a table and a graph Z versus Frequency, f is plotted.

Results:

f(kHz) VR (volts) VZ (volts) Z (ohm)

1 0.848 0.532 62.73585

2 0.65 0.79 121.5385

3 0.486 0.886 182.3045

4 0.387 0.941 243.1525

5 0.31 0.951 306.7742

6 0.262 0.969 369.8473

7 0.224 0.965 430.8036

8 0.189 0.943 498.9418

9 0.165 0.93 563.6364

Table 1.

Figure 1. Graph of f vs. Z

f(kHz) VR (volts) VZ (volts) Z (ohm)

10 0.143 0.911 637.0629

20 0.031 0.534 1722.581

30 0.003 0.329 10966.67

40 0.001 0.269 26900

50 0.001 0.316 31600

60 0.001 0.395 39500

Table 2.

Figure 2. Graph of f vs. Z

Discussion

Graph 1

1. In the first graph, the line cuts the x-axis at 5 ohm. Based on , the 5 ohm represents r where r is the internal resistance of the inductor.

2. Based on the graph, Z ( ) is proportional to f (kHz). In other words, impedance increases as frequency increases. Therefore, the unknown component is an inductor. Inductive reactance, XL is given by .

Graph 2

1. In the second graph, the impedance is plotted against a higher range of frequency. As frequency is high, r is negligible.

2. |Z| = r2 +

Since r = 0,

|Z| =

Therefore

|Z| / f = 2 L

Since |Z| / f is the slope, therefore

Slope = 2 L

Therefore

L = (slope/2 ) Henry

Conclusion:

The unknown component is an inductor. The internal resistance, r at the inductor is 5 . When the frequency is higher, r is negligible. The inductance, L is 146H.

Resonance

A circuit is said to be in resonance when its impedance is equal to its resistance. There are two types of resonant circuit: Series and Parallel.

2 types of resonant circuits are shown in the following 2 experiments.

Experiment 2: Series Resonance

Aim

All the passive elements are connected in series. The aim of this experiment is to investigate the properties of series resonace.

Procedure:

1) The conductor, C, inductor, L and...
tracking img