IGCSE 2020 Physics 0625/61 May/June

IGCSE 2020 0625/61 May/June (pdf)

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1. A student investigates the balancing of a metre rule.
   Fig. 1.1 shows the arrangement.
   (a) The student places the metre rule on the pivot at the 50.0cm mark. He places an object Q on the metre rule with its centre at the 90.0cm mark. He places a load of weight P = 2.0N on the metre rule and adjusts the position of the load so that the metre rule is as near as possible to being balanced.
   He measures the distance x from the centre of the load to the pivot.
   He repeats the procedure using loads of weight P = 3.0N, 4.0N, 5.0N and 6.0N. All the values of P and x are recorded in Table 1.1.
   Calculate, and record in Table 1.1, the values of 1/x.
   (b) Plot a graph of P/N (y-axis) against (x-axis). Start both axes at the origin (0,0).
   (c) In this experiment, x_max , the maximum possible value for x is 50.0cm. Calculate 1/ x_max.
   Use the graph to determine the minimum value of P required to balance the metre rule in this experiment. Show clearly on the graph how you determined this value.
   (d) In this experiment, the width of object Q is slightly greater than the width of the metre rule. Explain briefly how you would place the object Q as accurately as possible on the 90.0cm mark of the metre rule. You may draw a diagram.
   (e) In this experiment, it is difficult to determine the exact position of the load that will make the metre rule balance.
   (i) Explain briefly why this is difficult.
   (ii) Explain briefly how you would find the best position of the load that will make the metre rule balance.
   
2. A student determines the resistances of some filament lamps.
   Fig. 2.1 shows the first circuit she uses.
   (a) (i) Record the potential difference V₁ across the lamp L₁, as shown on the voltmeter in Fig. 2.2.
   (ii) Record the current I₁ in the circuit, as shown in Fig. 2.3.
   (iii) Calculate the resistance R₁ of the filament of lamp L₁. Use the equation R₁ = V₁/I₁. Include the unit.
   (b) The student disconnects the voltmeter. She connects lamp L₂ in series with lamp L₁. She connects the voltmeter across lamp L₂.
   She measures the current I₂ in the circuit and the potential difference V₂ across lamp L₂.
   Calculate the resistance R₂ of the filament of lamp L₂. Use the equation R₂ = V₂/I₂.
   The student disconnects the voltmeter. She connects lamp L₃ in series with lamps L₁ and L₂.
   She connects the voltmeter across lamp L₃.
   She measures the current I₃ in the circuit and the potential difference V₃ across lamp L3.
   Calculate the resistance R₃ of the filament of lamp L₃. Use the equation R₃ = V₃/L₃
   (c) Calculate R₁ + R₂ + R₃. Give your answer to a suitable number of significant figures for this experiment.
   (d) Some students make suggestions about the results of the experiment.
   Suggestion A: R₁ + R₂ + R₃ should be equal to 3 × R₁. Suggestion B: R₁ + R₂ + R₃ should be less than 3 × R₁. Suggestion C: R₁ + R₂ + R₃ should be greater than 3 × R₁.
   State which suggestion A, B or C agrees with your results. Justify your answer by reference to your results.
   (e) Draw a circuit diagram to show the circuit used in part (b) with all three lamps connected in series.

3. A student investigates the position of the image in a plane mirror.
   Fig. 3.1 shows the ray-trace sheet he uses.
   (a)

• The student draws the line MR.
• He draws a normal NL to this line that passes through the centre of MR.
• He labels the point at which NL crosses MR with the letter B.
• He draws a line from B at an angle of incidence i = 30° to the normal below MR and to the left of the normal. He labels the end of this line A.
• He places a pin P1 on line AB, as shown in Fig. 3.1. He places another pin P2 on the line AB.
• He places the reflecting face of the mirror vertically on the line MR.
• He views the images of pins P1 and P2 from the direction indicated by the eye in Fig. 3.1.
  (i) On Fig. 3.1, mark with a cross a suitable position for pin P2 in this experiment.
• He places two pins P3 and P4 some distance apart so that pin P3 and the images of P2 and P1 all appear exactly behind pin P4. The positions of P3 and P4 are shown on Fig. 3.1.
  (ii) Draw the line joining the positions of P3 and P4. Continue the line until it extends at least 7.0cm beyond MR.
  (b)
• The student keeps pin P1 in the same position but moves pin P2 so that the angle of incidence i = 40°.
• The pin positions P5 and P6 for the reflected ray are marked on Fig. 3.1.
  (i) Draw the line joining the positions of P5 and P6. Continue the line until it extends at least 7.0cm beyond MR.
  Label with the letter Y the point where the two lines cross beyond MR.
  (ii) Draw a line from P1 to MR that meets MR at a right angle. Measure and record the length a of this line.
  (iii) Draw a line from the point labelled Y to MR that meets MR at a right angle. Measure and record the length b of this line.
  (c)
• The student removes all the pins. He places pin P7 on the normal at a distance 6.0cm from the front of the mirror.
• He views the image of P7 in the mirror.
• He places pin P8 on the normal behind the mirror.
• He adjusts the position of P8 so that the image of the bottom of the pin P7 and the top of pin P8 seen over the mirror appear as one pin when viewed from all angles in front of the mirror.
  (i) On Fig. 3.1, measure the distance x along the normal between P8 and the mirror.
  (ii) Complete the diagram in Fig. 3.2 to show the appearance of the image of pin P7 and pin P8 as described in (c).
  (d) The student expects the readings to show that the image formed in a plane mirror is the same distance behind the mirror as the object is in front of the mirror. Readings of a = b and x = 6.0cm will show this.
  State whether your readings show that the image formed in a plane mirror is the same distance behind the mirror as the object is in front of the mirror. Justify your statement by reference to the readings.
  (e) The student carries out this experiment with care. Suggest a practical reason why the results may not be accurate.
  

4. A student investigates the effect of the colour of the surface of a metal container on the rate of loss of heat from the container. She knows that black surfaces are better radiators of thermal energy than white surfaces and wants to investigate the effect of other colours.
   The following apparatus is available:
   metal containers each with the outer surface painted a different colour
   a thermometer
   a stop-watch
   a supply of hot water.
   She can also use other apparatus and materials that are usually available in a school laboratory.
   Plan an experiment to investigate the effect of the colour of the surface of a metal container on the rate of loss of heat from the container.
   You should:

• draw a diagram of the apparatus used
• explain briefly how you would carry out the investigation
• state the key variables to be kept constant
• draw a table, or tables, with column headings, to show how you would display your readings (you are not required to enter any readings in the table)
• explain how you would use your readings to reach a conclusion.

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