826 words - 3 pages

EM6 Internal Resistance and EMF of a Battery CellDCPAspect 1Symbols:Internal resistance of the battery: rExternal variable resistor: RVoltage: VEMF of the battery: ECurrent: IFormulaV= IRE = I (R+r)E = IR +I ⋅ rE = V + I ⋅ rV = E - I ⋅ rV = -r ⋅ I +EGraph of V against I will be plotted in order to determine the internal resistance and EMF of the battery. The slope will be -r and the intercept vertical axis will be the EMF (E).Reference Value

EMF of the battery

1. 490 ± 0.001V

Aspect 2 & 3Data Collection and Processing

Obs. No.

Voltage

Current

± 0.01V

± 0.1A

1

0.42

1.7

2

0.54

1.5

3

0.62

1.3

4

0.66

1.2

5

0.80

0.9

6

0.90

0.7

7

0.94

0.6

8

1.10

0.4

9

1.20

0.3

Figure 1 Voltage against CurrentCEVCalculationThe Internal resistance of the batteryUncertainty for SlopeFrom the graph above (Voltage against Current)Slope of the best-fit line= - 0.5223 Ω (from the graph)S1 = maximum slope = - 0.4714 Ω (from the graph)S2 = minimum slope = - 0.6429 Ω (from the graph)ΔS = |S1 - S2| / 2= | (-0.4714 - (-0.6429)) | / 2= 0.08580 Ω (cor. to 4 sig. fig)The internal resistance of the battery ± Δ Internal resistance of the battery = 0.5223 Ω ± 0.08580 Ω (cor. to 4 sig. fig)Percentage precision= (1.000 - 0.08580 /0.5223) x 100% = 83.57% (cor. to 4 sig. fig)The EMF of the batteryUncertainty for intercept vertical axisFrom the graph above (Voltage against Current)Intercept vertical axis of the best-fit line = 1.2969 V (from the graph)y1 = Intercept vertical axis of the maximum slope = 1.2414 V (from the graph)y2 = Intercept vertical axis of the minimum slope = 1.4929 V (from the graph)Δy = |y1 - y2| / 2= | (1.2414V - 1.4929V) | / 2= 0.25150 V (cor. to 5 sig. fig)The EMF of the battery ± Δ EMF of the battery = 1.2969 V ± 0.25150V (cor. to 5 sig. fig)Percentage precision= (1.0000 - 0.25150/1.2969) x 100% = 80.61% (cor. to 4 sig. fig)Percentage accuracy= (1.0000 - (1. 4900 - 1.2969 /1. 4900)) x 100% = 87.05% (cor. to 4 sig. fig)Conclusion and EvaluationAspect 1Conclusion

The Internal resistance of the battery

0.5223 Ω ± 0.08580 Ω (cor. to 4 sig. fig)

Percentage precision

83.57% (cor. to 4 sig. fig)

The EMF of the battery

1.2969V ± 0.25150V (cor. to 5 sig. fig)

Percentage precision

80.61% (cor. to 4 sig. fig)

Percentage accuracy

87.05% (cor. to 4 sig. fig)

The percentage precision of measuring the internal resistance of the battery is 83.57%, with the...

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