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Physics Paper 1, MAy/June. 2009  
Questions: 1 2 3 4 5 6 Main


General Comments
Weakness/Remedies
Strength

 

 

 

 

 































 

 

 

 

 

 

 

 

 

 

 

Question 6

(a)   Diagram

You are provided with a cell E, standard resistor R, bare constantan wire W, key K, voltmeter V and crocodile clips.

    1. Connect the two ends of the wire W to the same point T of the plug key K so that W forms a loop.
    2. Connect the rest of the circuit as shown in the diagram above.
    3. Using the crocodile clip, grip a point B on the bare wire such that BT = l = 15 cm.
    4. Close the key K and measure the potential difference VƖ across the wire and VR across the standard resistor R.
    5. Evaluate V = V1
                        VR
    6. Repeat the procedure for other values of l = 30, 40, 50, 60 and 70 cm.  in each case, measure V1, VR and  evaluate V  =  V1
                                                        VR
    7. Plot a graph of V on the vertical axis and l on the horizontal axis.
    8. .Draw a smooth curve through the points.
    9. Record the maximum value M, for V and the corresponding value of l.
    10. State two precautions taken to ensure accurate results.

                              
(b)(i)    Explain how heating affects the results of experiment.                                       

    (ii)    How can the effect of heating be reduced practically in the experiment?           
_____________________________________________________________________________________________________
Observation

This question was fairly answered by most candidates.  However, many failed to get the trend of VL correctly, probably candidates did not make wire into a loop as demanded by the question.

The (b) part was not well attempted.  

In part (a) the candidates were expected to: 
         

    measure and record to1 decimal place six value of l;

    (iii)read and record to  1 decimal place six values of Vi ;  (Trend: as l increases,Vi increases then decreases)

(iv)read and record to 1 decimal place six values of VR ;

  (v) evaluate  six values of ;    Vi      ;          
                                                       VR                 

    (vi) record data in a composite table showing Ɩ, VƖ,   VR,     and   Vl /  VR ;                       
     (vii)       indicate the graph axes, select reasonable scales, plot six points;
 
     (viii)      draw a smooth curve through the points;

  •  show and record the maximum value of M and the corresponding value of l;

(x)         state any two of the following precautions in acceptable form:
                  Ensured tight connections/ clean terminals

  • Removed key after each reading
  • Avoided parallax error in reading voltmeter
  • Evidence of repeated readings
  • Noted and corrected for zero error of voltmeter/meter rule.

(b)(i)    Effects of heating on the experimental results

  • The constantan wire will increase in length (expand) and length of the loop increases. Consequently the value of Ɩ increases.                                                         
  • The resistance of the wire increases                                                                
  • To reduce the effect of heating, remove the key immediately after taking each reading


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