EV101_sen_lab_001_May14

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FACULTY OF ENGINEERING, ARCHITECTURE & BUILT ENVIRONMENTSCHOOL OF ENGINEERING

EV101 ELECTRICAL PRINCIPLES

Experiment 1Ohm’s Law to a Resistor

Objective: To test Ohm’s Law by plotting V vs I for a resistor. To become familiar with the voltmeter – ammeter methods for measuring

resistance, voltage, and current.

Apparatus and components:

1. Resistor: 1 k .2. Breadboard.3. DC power supply.4. Multimeter.5. Jumpers/cables/connectors.

Background theory:

Relation between currents which are flowing through an electrical or electronicdevice/component and voltages across the device/component, as depicted in Fig. 1.1, isvery important. The resistance value of a resistor is depending on the length, l, the surfacearea, A, and the resistivity, of its material to the current.

(i) Resistance vs conductor’s size. (ii) Current and voltage relationship on the resistor.

Fig. 1.1. The principles of resistance.

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Relation between resistor (R), current (I), and voltage (V) is stated by Ohm’s law as

I=V/R ……………………….. (1.1)

Equation (1.1) can be represented as a linear straight line of voltage vs current graph, asdepicted in Fig. 1.2. The slope of the line is proportional to the inverse of the resistor.

Fig. 1.2 Voltage vs current (Ohm’s law)

Procedure:

1. Build a circuit shown in Fig. 1.3 on the breadboard.

Fig. 1.3 Proving Ohm’s law on a resistor.

2. Measure the value of resistor, R, shown in Fig. 1.3 before switch ON the dc power supply.Record the measurement results into Table 1.1.

3. Calculate current, I, flows in circuit of Fig. 1.3. Record the results in Table 1.1.

4. Switch ON dc power supply and set the output voltage, E, equal to 1 V.

5. Measure the voltage across the resistor, RV , of the circuit in Fig. 1.3 using Voltmeter. Use

the Voltmeter in appropriate range. Record the measurement results into Table 1.1.

6. Measure the current flowing in the circuit using Ammeter and record the measurementresults into Table 1.1. Don’t forget to set the Ammeter in appropriate range.

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7. Re-do step 3 to 5 for each output voltage of dc power supply, E, given in Table 1.1.Record the results.

Table 1.1 Calculation and measurement data for proving Ohm’s law on resistor.

R (theory)= 1 k R (measured) = …..

E (set values) I (calculated) V (measured) I (measured)1 V2 V3 V4 V5 V6 V7 V8 V9 V

10 V11 V12 V13 V14 V15 V

8. Plot the graph of V vs I on Fig. 1.4 for;(i). E (set values) vs I (calculated)(ii). V (measured) vs I (measured).

Fig. 1.4 I vs V on Resistor

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9. Calculate the slope of the graph and the value of resistor in Fig. 1.4.

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Discussion:

Conclusion: