Internal Resistance of A Battery Lab1

 

Physical Sciences Prescribed Experiment for formal Ass Assessment essment Knowledge Area: Electricity and Magnetism Topic: Internal resistance and Series-Parallel networks Part 1 Aim To determine the internal resistance of a battery Precautions Do not leave the switch closed closed at all times. The battery will run flat. Close the switch switch only for taking the readings on the voltmeter and Ammeter Ammeter.. Take your readings accur accurately ately.. Do not conduct the experiment with wet hands. Instructions Place 4 x 1,5V cells in a cell holde Place holderr in a serie series s connec connection. tion. Conn Connect ect a Switch, Amme Ammeter ter and a Rheostat in series to the battery. Connect the V Voltmete oltmeterr across the battery. If a rheostat is not available, resistors or bulbs could be used in the place of a rheostat. The resistors or bulbs must be connected connected in series. One resistor/bulb must be co connected nnected first and then the resistors/bulbs be increased to two in series, three in series, etc. Draw the electrical circuit diagram. Set the Rheostat at 10 . Close the switch and reduce the resist res istanc ance e in the Rhe Rheost ostat at ste step p by ste step, p, inc increa reasin sing g the cur curren rentt at the sam same e tim time. e. Take the ammeter and voltmeter readings in each case/step. Open the switch while recording the readings in order to spare the batteries’ life span. Take and record a minimum of 5 readings. Interpret and analyse the data in order to determine the internal resistance. Write a conclusion and prepare a report (write-up). Part 2 Aim: 1. To determine the equivale equivalent nt resistance in a Series-parallel n network etwork electrical circuit. 2. To compare the experimenta experimentall values of the equivale equivalent nt resistance to the th theoretical eoretical values. Instructions: Place 4 x 1.5V cells in a cell in a cell holder in a series connection. Connect a voltmeter (V 1) across the battery. Connect three resistors of different resistance. One resistor must be connected in series with a voltmeter (V 2) across and the other two resistors must be connected in parallel with a voltmeter across (V3). Connect a switch and an ammeter ammeter.. Draw the electrical circuit. Determine the equivalent resistance experimentally and compare the readings to the calculated values of equivalent resistance. Submit a report (write up) 1

 

Part 1 Possible Marking Memorandum and Rubric Internal resistance Topic:  Internal resista Topic:  resistance nce and Series-parallel n networks. etworks. Aim: To Aim:  To determine the internal resistance of a battery. Apparatus:

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 4 (Size RD) 1.5V cells   Voltmeter    Ammeter   10 Rheostat or Resistors or Bulbs  Connecting wires  Cell holder   Switch

Precautions: Do not leave the switch closed closed at all times. The battery will run flat. Close the switch only only for  taking the readings on the voltmeter and Ammeter. Take your readings accurately Method: STEP Procedure 1 4 cells, 1,5V each were placed in a cell holder and connected in series.   2  A switch switch was connected to th the e positive terminal of the battery. battery.  

(1)

3

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The negative terminal of the ammeter was connected to the one end of the switch.

(1)



4

 A rheostat was set at 10 and its negative terminal was connected to the positive terminal of the ammeter. Its positive terminal was connected to the negative terminal

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of the battery.  5 6

 A voltmeter voltmeter was connected in p parallel arallel across the battery Electrical circuit:  Allocate one mark for each   V

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component of electrical the circuit drawn and connected correctly.



 

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r 



   

A



That is: The voltmeter voltmeter,,  Ammeter,, Rheostat, switch  Ammeter and the battery  with  with internal resistor.



NB: Resistors/ bulbs con connected nected in series c could ould be used in the place of a rheostat, startin sta rting g wit with h one bu bulb/ lb/res resist istor or and inc increa reasin sing g the res resist istanc ance e aft after er tak taking ing an and d recording the readings 2

 

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The switch switch was closed closed.. The amme ammeter ter and the volmete volmeterr reading readings s were taken and

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8

recorded when the rheostat was set at 10. The resistance in the rheostat was reduced five times and each case a volmeter and

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9

the ammeter readings were taken and recorded.  The switch was closed to take the readings and it was opened immediately after  (1) taking the readings.  

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Results: Results: (NB: the results below are hypothetical and illustrative. The learners must be assessed on their recorded results accordint to the experiment conducted.) I (A)

VT(V)

0

6

0.6

5.76

1.2

5.52

1.8

5.28

2.4

5.04

1. 2. 3.

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 Tabulating results Labelling Columns (Quantity with units)  Correct Experimental values

Interpretation and analysis: Graph

1. 2. 3. 4.

Suitable caption Labelled axis

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Calibration Calibratio n on the t he axis Shape of the graph

Gradient is the internal resistance and therefore:

Conclusion:  The y-intercept of the graph is the EMF.  The x-intercept of the graph is the maximum electrical current (I). The gradient or slope of the graph is the internal resistance (r) = 0,42   Grand total

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

35

4

 

Part 2 Possible Marking Memorandum and Rubric Equivalent resistance   Comparing experimental equivalent resistance values to theoretical values Topic: Equivalent resistance in series-parallel circuits Topic: Aim:: To Aim To determine the equivalent resistance in series-parallel electrical cir circuits cuits   To compare experimental values of the equivalent resistance to theoretical values. Apparatus: Apparatus:  4(RD) 1,5V cells  Cell holder   Switch  3 Voltmeters   Ammeter   3 resisters (different sizes)  Connecters Precautions:: Precautions Do not conduct conduct the experiment experiment with wet hands. Ensu Ensure re that the ammeter and the voltme voltmeter ter are connected together. If the bulbs are used in place of resistors, the current (amperes) and the voltage labelled on the bulbs should be taken into account. Method STEPS PROCEDURE 1 4 cells (1,5V each) were placed in i n a cell holder and were connected in series.   (1) 2

The switch was connected to the positive side of the battery. battery. 

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3

The negative terminal of the ammeter was connected to the switch in series.  

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4

One resistor was connected to the positive terminal of the ammeter in series. 

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5

Two resistors were connected in parallel and connected to the other resistor resistor..   Volmeters, V1, V2 and V3 were connected across the battery, a resistor in series

(1)

6

(1)

and the parallel combination of resistors, respectively respectively..   7

   

V1





(9)  Allocate one mark for each component of electrical the circuit drawn and connected correctly.

r 



  A  

  R1

 

That is: Each voltmeter voltmeter,,  Ammeter,, each external  Ammeter resistor,, switch and the resistor battery  with  with internal resistor.

R2 

R3

V   2

 

V



3

5

 



 

8

The switch was closed, the reading on the ammeter and the voltmeters were

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taken and recorded.  Results: NB: The values are hypothetical

EMF (V1) 6V

Terminal voltage (V1)

V2

V3

I

Internal resistance

6