Sec 4 AST, ST, EST/Electricity/ Resistance Name:________________________________

Factor affecting the resistance of a conductive wire

A) Resistance versus the thickness (Gauge) of a conductive wire.Material:

Nichrome wire #26, #22 and #18 2 Alligator wires Ammeter (Reading on the power pack) Voltmeter (Reading on the power pack)

Procedure:1) Set power pack to 3V2) Use 80cm long of the selected wire gauge (#26, #22 or #18)3) Connect the terminal of the power pack to the wire4) Read and record the Voltage (V) and Current (I) in ampere (Amp)5) Calculate the resistance in ohm using the formula: R= V/I6) Make a graph showing the relationship between the Resistance and the Gauge

(thickness) of the Nichrome wire.*Note: The higher the Gauge number the thinner the wire.

Results:_______________________(title)

V(volts) I (Amp) R (Ω)Nichrome #26Ø = 0.4mmNichrome #22Ø : 0.65mmNichrome #18Ø : 1.02mm

B) Resistance versus length of a conductive wireMaterial:

Power pack with Volt and Current reading. Nichrome wire #18 2 alligator wires Nichrome wire gauge #18

Graph: Resistance(Ω) versus Length(m) Procedure:

1) Set the voltage to 1.5V2) Connect the Nichrome wire to the power pack3) Record the Current reading for length 0.80m, 0.40m and 0.20m

Results: Resistance/length: Nichrome wire #18

Graph: Resistance(Ω) versus Length(m)

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C) Does the material a wire is made of affect its resistance?

Material: 2 wires (Fe and Nichrome) Gauge#26

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V(volts) I (Amp) R (Ω)80cm40cm20cm

2 Alligator wires Ammeter (Reading on the power pack) Voltmeter (Reading on the power pack)

Procedure:1) Set power pack to 1.5V2) Use 80cm long of the selected wire gauge3) Connect the terminal of the power pack to the wire4) Read and record the Voltage (V) and Current (I) in ampere5) Calculate the resistance in ohm using the formula: R= V/I

Results:____________________________________________(title)

Length (cm) Volts (V) I (Amp) Resistance(Ω)

Iron wire

Nichrome wire

Conclusion:How is the resistance of a wire affected by the three factors investigated?

Activity 2: Resistor colour code / multi-meter readings

Note: 1- Count the number of bands first. 2- Use the resistor color code chart.

Act # 1 : Use the color code to determine the resistance of 3 resistors.

Band 1st 2nd 3rd 4th 5th 6th Value(Ω)

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Resistor #

Act#2 -resistance value using the multimeterDetermine the value of the resistor of the 3 resistors using the multimeter.

Table of results:Resistor# range Reading Resistance (Ω)

Conclusion/discussion How does the resistance determine with the resistor color-coding chart compare with the resistor resistance value measured by the multi-meter? Are the measured resistance within the specified tolerance value?

Info:Equation representing the dependency of the resistance (R) of a cylindrically shaped conductor (e.g., a wire) upon the variables that affect it is:

R=ρ LA

Resistivity in (ohm•meter) for a few materials

Measuring the resistance with a digital multi-meter.

The multi-meter you are using is a battery-operated digital type that reads out in digits on an LCD (liquid crystal display) screen. The meter is read using the appropriate scale: DC volts (DC V), AC volts (AC V), Ohms(Ω), or DC amperes or

L represents the length of the wire (in meters), A represents the cross-sectional area of the wire (in meters2), and ρ represents the resistivity of the material (in ohm•meter)

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Material Resistivity (ohm•meter)Silver 1.59 x 10-8

Copper 1.7 x 10-8

Iron 10 x 10-8

Nichrome 150 x 10-8

Glass 1010 - 1014

Hard Rubber 1013

2000k

Black lead Red lead ( V, Ω, MA)

Note: Use the resistor #3 as an example. 1. Take the resistor #32. Set the dial for the Resistance reading Ω 3. Choose the largest scale: 2000K (2 000 000 Ω )4. Place the resistor on the little foam mat.5. Place the probes (red and black) on each of the resistor’s #3 terminals

You should get a reading:

1Scale: 2000K: Only a 1 on the left: the circuit is open: No readingSolution: check the connections (if still no reading, the resistor is more than 2000000Ω)

0 0 0Scale 2000K You get a reading, however the first, second or all digits are 0’sGet a more precise reading by selecting the next smaller scale (200K)

0 0. 3

Scale 200K: You get a reading, however the first, second or all digit are 0’sGet a more precise reading by selecting the next smaller scale (20K)

0. 2 7Scale 20K You get a reading, however the first, second or all digit are 0’sGet a more precise reading by selecting the next smaller scale (2000 Ω).

2 7 3 Scale 2000 Reading: 273 Ω The resistance is

1Scale 200 : Only a 1 on the left: No reading : the scale chosen is too low.This scale (200 Ω) measures resistance up to 200 Ω.

The multi-meter you are using is a battery-operated digital type that reads out in digits on an LCD (liquid crystal display) screen. The meter is read using the appropriate scale: DC volts (DC V), AC volts (AC V), Ohms(Ω), or DC amperes or

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