Year 11 Physics I.D

Year 11 Physics I.D.

Time allowed: 45 minutes Mark _____ / ______

· Write your name or student I.D. on each page.

· Pages 2 and 3 must be collect separately after you complete page 1.

· Questions 1 will require you to work in a group of 3 at one of the workstations located around the outside of the room. The practical component of this question should take you no more than 6 minutes to complete.

· Questions 2 – 5 are to be completed individually

· Answer all questions in the spaces provided.

· Formulas and Data

Energy = VIt P=VI R = V/I E = cmT

Specific heat of water, c = 4200 J kg-1 K-1

1. In this task, you will work in groups of three. You are provided with two lamps labelled A and B, a transformer set on G (~12 V) and some connecting wires.

(a) Wire the two lamps in series and then in parallel and observe their brightness. Record your observations in an appropriate way in the space below. (3 M)

(spend no more than 6 minutes on this activity)

Collect pages 2 and 3 for question 1 from the front bench and then return to your seat. The remainder of question 1 must be completed individually.

(b) Compare the brightness of lamp A when it is connected in series with when it is connected in parallel. (1 M)

(c) Identify which lamp has the higher resistance. Justify your answer with specific reference to the observations made in part (a). (3 M)

(d) (i) With reference to the formula P = VI, explain the observed difference in brightness of light B when it is connected in series compared with its being connected in parallel. (2 M)

(ii) With the aid of circuit diagrams, propose a procedure to obtain the measurements necessary to verify your explanation in part (i). (2 M)

Complete the following questions in the spaces provided. Don’t forget to collect pages 1 and 2 after you have completed page 1 (first-hand investigation in groups)

2. The photographs below show two views of a meter used in an electrical circuit.

Photograph 1 /
Photograph 2

(a) Record the reading shown by the meter. (1 M)

(b) For a measurement to be valid, it must be both accurate and reliable.

(i) Identify which photograph allows you to make the most accurate reading. Justify your answer. (1 M)

(ii) Outline what must be done in the experiment to ensure that the measurement of the current is reliable. (1 M)

3. During the topic on electricity, you performed an investigation of the heating of water using electrical energy. The equations E = VIt and E= mcT were required for the analysis. The following data was collected by a group of students performing the same experiment in which it took 5 minutes to heat the water.

Mass of water: 200 g Initial water temperature: 220C

Current measured: 2.2 A Final water temperature: 300C

Voltage measured: 10 V

(a) Calculate the electrical energy input. (2 M)

(b) When the students analysed their results, they realised that they must have made a mistake. Explain why. (2 M)

(c) A second group of students also performed the same investigation using a coil of wire as a heating element. The photographs below show the coil when they first performed the experiment (photograph 1) and when they repeated it (photograph 2). All variables, including using the same coil, were kept constant except for the change evident in the photographs.

Photograph 1 /
Photograph 2

(i) What were the students attempting to demonstrate by repeating the investigation? (1 M)

(b) Identify the variable that has been changed in the investigation. (1 M)

4. The table below shows how the current through a resistor changes when different voltages are applied across it by changing the voltage selection knob on the power supply (from A to F settings)

Setting / Off / A / B / C / D / E / F
Voltage (V) / 0 / 1.45 / 3 / 4.5 / 6 / 8 / 9.5
Current (A) / 0 / 0.33 / 0.92 / 0.98 / 1.38 / 1.85 / 2.22

(a) Plot an appropriate graph of this data and describe the relationship between voltage and current suggested by your graph. (4 M)

(b) One of the current readings was subsequently discovered to have been incorrectly recorded. Identify the incorrect reading and propose what the current value would most likely to have been based on the graph you have drawn. (2 M)

5. The heat produced when a current flows through a wire depends on the voltage applied and the current that flows through the wire. For a given voltage, the current is proportional to the resistance of the wire. The resistance also depends on several other variables. Each type of material has resistive properties that are unique to that material. For any given material, the resistance is proportional to the length of the conductor if no other variables are changed. It is also proportional to the wire’s temperature and inversely proportional to the square of the radius of the wire.

A 1 m length of copper wire has a resistance of 1.8 ohms when a voltage of 6 V is applied to it.

(a) Calculate the resistance a 1.5 m length of the same wire with the same applied voltage. (1 M)

(b) Calculate the resistance of a 2 m length of copper wire with a radius twice that of the original wire. (2 M)

End of Paper

Page 10 Practical and Processes Assessment Task 2006 £

Year 11 Physics I.D.

Marking Criteria

1 a)

Criteria / Marks
Results recorded in a well-constructed table with appropriate headings; correct, succinct qualitative observations made which clearly distinguish differences in brightness of lamps when connected in series and parallel / 3
correct, succinct qualitative observations made which clearly distinguish differences in brightness of lamps when connected in series and parallel but table used is poorly constructed / 2
correct, succinct qualitative observations made which clearly distinguish differences in brightness of lamps when connected in series and parallel but no table is used to present the observations / 1

Criteria / Marks
Clearly outlines one relevant difference between the brightness of the lamp referring to both series and parallel connections; response written as a comparison (preferably one sentence with appropriate “linking” word. / 1

Criteria / Marks
Correctly identifies lamp B; justification refers to specific, relevant observations and clearly links these to differences in the current through and voltage across the globes in either the series circuit or the parallel circuit / 3
Correctly identifies lamp B; justification refers to specific, relevant observations but does not clearly link these to differences in the current through and voltage across the globes in either the series or parallel circuits. / 2
Correctly identifies lamp B / 1

d (i)

Criteria / Marks
Clearly identifies that the observed brightness of the globe depends on both the current through and potential difference across it and relates this to any observed difference in brightness (will need to refer to their specific results) / 2
Identifies that the observed brightness of the globe depends on both the current through and potential difference across it / 1

d(ii)

Criteria / Marks
Draws two circuit diagrams which show a voltmeter and ammeter correctly connected to measure current through and potential difference across the light globe connected in series and in parallel and outlines the need to obtain these measurements to verify answer to part (i) / 2
One correct circuit diagram drawn and outlines the need to obtain these measurements to verify answer to part (i) OR Draws two circuit diagrams which show a voltmeter and ammeter correctly connected to measure current through and potential difference across the light globe connected in series and in parallel but does not clearly outline the need to obtain these measurements to verify answer to part (i) / 1

2 a)

Criteria / Marks
Identifies the reading as 2.4 A (unit should be present but no penalty if missing) / 1

b (i)

Criteria / Marks
Identifies photograph 1 and outlines that this view allows the measurement to be taken with minimal parallax error. (marks only awarded with a reasonable justification) / 1

b (ii)

Criteria / Marks
States that the experiment must be repeated / 1

3 a)

Criteria / Marks
Identifies the correct formula (E = VIt) and substitutes appropriately to calculate a correct final answer (6600 J) – no unit penalty / 2
Identifies the correct formula but substitutes incorrectly (eg fails to convert units of time) / 1

Criteria / Marks
Identifies through calculation that the electrical energy input is less than the heat energy absorbed by the water (6600 J to 6720 J) and that this contradicts the law of conservation of energy. / 2
Identifies through calculation that the electrical energy input is less than the heat energy absorbed by the water (6600 J to 6720 J) but does not clearly link this to the law of conservation of energy OR identifies that the results contradict the law of conservation of energy but do not perform an appropriate calculation to demonstrate this. / 1

c (i)

Criteria / Marks
Identifies that students were trying to establish reliability / 1

Criteria / Marks
Identifies that the length of wire submerged has been changed / 1

Criteria / Marks
States that the water in photograph 2 would not have increased in temperature by as much as the water in photograph 1 and clearly links this to heat loss into the air due to the exposure of much of the element / 3
States that the water in photograph 2 would not have increased in temperature by as much as the water in photograph 1 but does not clearly link this to heat loss into the air due to the exposure of much of the element. / 2
States that the water in photograph 2 would not have increased in temperature by as much as the water in photograph 1 / 1

4 a)

Criteria / Marks
Graph with a heading, labelled axes and units, a scale which uses more than half the graph paper, correctly plotted points and a reasonable straight line of best fit. Correctly identifies the relationship as voltage being directly proportional to the current. / 4
Missing one of the above / 3
Missing two of the above / 2
Missing three of the above / 1

Criteria / Marks
Identifies the correct point (3, 0.92) and correctly reads the point from the line of best fit (3, 0.7) / 2
Identifies the correct point OR correctly reads the point from the line of best fit / 1

Criteria / Marks
Identifies that current is the dependent variable / 1

5 a)

Criteria / Marks
Correctly calculates the resistance as 2.7 ohms (1.5 x 1.8) / 1

Criteria / Marks
Correctly calculates new resistance as 0.9 ohms by linking effect of length and radius on overall resistance (resistance is proportional to length but inversely proportional to radius squared) / 2
Correctly calculates effect of length OR radius on resistance but overall calculation incorrect / 1

Page 10 Practical and Processes Assessment Task 2006 £