Four of the appliances, including the fan heater, are designed to transform electrical energy into heat.

Transcription

1 The pictures show six different household appliances. (a) Four of the appliances, including the fan heater, are designed to transform electrical energy into heat. Name the other three appliances designed to transform electrical energy into heat. 2 3 (3) Page of 20

2 (b) The bar chart shows the power of three electric kettles, X, Y and Z. Kettle (i) In one week, each kettle is used for a total of 30 minutes. Which kettle costs the most to use? Put a tick ( ) next to your answer. X Y Y () (ii) A new express boil kettle boils water faster than any other kettle. Draw a fourth bar on the chart to show the possible power of an express boil kettle. () Page 2 of 20

3 (c) The graph shows how the time to boil water in an electric kettle depends on the volume of water in the kettle. Volume of water in litres A householder always fills the electric kettle to the top, even when only enough boiling water for one small cup of coffee is wanted. Explain how the householder is wasting money. (3) (Total 8 marks) Page 3 of 20

4 2 Figure shows a circuit diagram containing two identical lamps arranged in parallel. The reading on the ammeter is 86 ma. Figure (a) Which statement about the current through the lamps is true? Tick one box. The current through both lamp P and lamp Q is A The current through both lamp P and lamp Q is 0.86 A The current through both lamp P and lamp Q is 0.93 A The current through both lamp P and lamp Q is.86 A () Page 4 of 20

5 (b) One of the lamps breaks and is not replaced. Which statement about the current in the other lamp is true? Tick one box. The current through the lamp is A The current through the lamp is 0.86 A The current through the lamp is 0.93 A The current through the lamp is.86 A () (c) Figure 2 shows a circuit that can be used to alter the brightness of a lamp. Figure 2 The resistance of the variable resistor is increased. What effect will this have on the brightness of the lamp? Explain your answer. (2) (d) When the potential difference across the lamp is 3.3 V, the current is 0.5 A. Write down the equation that links current, potential difference and resistance. Equation... () Page 5 of 20

6 (e) Calculate the resistance of the lamp. Resistance =... Ω (3) (f) Sketch a current potential difference graph for a filament lamp. 3 (a) The diagram shows the circuit used to obtain the data needed to plot the current potential difference graph for a filament bulb. () (Total 9 marks) (i) Why is the component labelled J included in the circuit? () Page 6 of 20

7 (ii) The resistance of the bulb increases as the potential difference across the bulb increases. Why? () (iii) The bulb is at full brightness when the potential difference across the bulb is 2 V. The current through the bulb is then 3 A. Calculate the power of the bulb when it is at full brightness and give the unit. Power =... (3) Page 7 of 20

8 (b) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. The table gives data about two types of light bulb people may use in their homes. Type of light bulb Energy efficiency Cost of one light bulb Average lifetime in hours Halogen 0% Light Emitting Diode (LED) 32% Both types of light bulb produce the same amount of light. Evaluate, in terms of cost and energy efficiency, the use of the two types of light bulb. To gain full marks you must compare both types of light bulb and conclude which light bulb would be the best to use. (6) (Total marks) Page 8 of 20

9 4 A student is investigating some electrical components. (a) Describe how the student could set up a circuit to find the resistance of a lamp. You should include a circuit diagram in your answer. (4) Page 9 of 20

10 (b) The student is given an electrical component in a sealed box. She has to find out what the electrical component is by experiment. The student records the current and the potential difference for the component. Her results are shown in the figure below. Explain how the student could know that the electrical component in the sealed box is not an ohmic conductor. (2) Page 0 of 20

11 (c) What is the electrical component in the sealed box? Explain your answer. Component... Explanation... (3) (d) Use the graph to determine the resistance of the component at 2.3 V. Resistance =... Ω (4) (Total 3 marks) Page of 20

12 5 Table shows information about different light bulbs. The bulbs all have the same brightness. Table Type of bulb Input power in watts Efficiency Halogen Compact fluorescent (CFL) LED (a) (i) Calculate the useful power output of the CFL bulb. Useful power output =... watts (2) (ii) Use your answer to part (i) to calculate the waste energy produced each second by a CFL bulb. Waste energy per second =... joules () Page 2 of 20

13 (b) (i) A growth cabinet is used to investigate the effect of light on the rate of growth of plants. The figure below shows a growth cabinet. In the cabinet the factors that affect growth can be controlled. A cooler unit is used to keep the temperature in the cabinet constant. The cooler unit is programmed to operate when the temperature rises above 20 C. The growth cabinet is lit using 50 halogen bulbs. Changing from using halogen bulbs to LED bulbs would reduce the cost of running the growth cabinet. Explain why. (4) (ii) A scientist measured the rate of growth of plants for different intensities of light. What type of graph should be drawn to present the results?... Give a reason for your answer. () Page 3 of 20

14 (c) Table 2 gives further information about both a halogen bulb and a LED bulb. Table 2 Type of bulb Cost to buy Lifetime in hours Operating cost over the lifetime of one bulb Halogen LED A householder needs to replace a broken halogen light bulb. Compare the cost efficiency of buying and using halogen bulbs rather than a LED bulb over a time span of hours of use. Your comparison must include calculations. (4) (Total 2 marks) Page 4 of 20

15 Mark schemes (a) iron hairdryer kettle (b) (i) Y answers can be in any order (ii) bar drawn with any height greater than Y ignore width of bar (c) (bigger volume) takes more time (to boil) accept explanation using data from graph (so) more energy transferred do not accept electricity for energy (and) this costs more money ignore reference to cost of water wasting more money because heating more water than needed is insufficient [8] 2 (a) A (b) A (c) (increasing the resistance) decreases the current therefore (the lamp will be) dimmer (d) potential difference = current resistance accept correct rearrangement with R as subject (e) 3.3 = 0.5 R R = 3.3 / 0.5 (Ω) Page 5 of 20

16 R = 22 (Ω) allow 22 (Ω) without working shown for 3 marks (f) line drawn from the origin with a decreasing gradient. [9] 3 (a) (i) to obtain a range of p.d. values accept increase / decrease current / p.d. / voltage / resistance accept to change / control the current / p.d. / voltage / resistance to provide resistance is insufficient a variable resistor is insufficient do not accept electricity for current (ii) temperature of the bulb increases accept bulb gets hot(ter) accept answers correctly expressed in terms of collisions between (free) electrons and ions / atoms bulb gets brighter is insufficient (iii) 36 allow mark for correct substitution, ie 2 3 provided no subsequent step shown 2 watt(s) / W accept joules per second / J/s do not accept w (b) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the information in the Marking guidance, and apply a best-fit approach to the marking. 0 marks No relevant content. Level (-2 marks) There is a basic comparison of either a cost aspect or an energy efficiency aspect. Page 6 of 20

17 Level 2 (3-4 marks) There is a clear comparison of either the cost aspect or energy efficiency aspect OR a basic comparison of both cost and energy efficiency aspects. Level 3 (5-6 marks) There is a detailed comparison of both the cost aspect and the energy efficiency aspect. For full marks the comparisons made should support a conclusion as to which type of bulb is preferable. Examples of the points made in the response: cost halogen are cheaper to buy simply giving cost figures is insufficient 6 halogen lamps cost the same as one LED LEDs last longer need to buy 8 / more halogen lamps to last the same time as one LED 8 halogens cost 35.0 costs more to run a halogen than LED LED has lower maintenance cost (where many used, eg large departmental store lighting) energy efficiency LED works using a smaller current LED wastes less energy LEDs are more efficient LED is 22% more energy efficient LED produces less heat LED requires smaller input (power) for same output (power) 6 [] Page 7 of 20

18 4 (a) (b) (c) (d) ammeter connected in series voltmeter connected in parallel measure the potential difference across the lamp at known current calculate resistance from measured values using V = IR for ohmic conductors the current is directly proportional to the potential difference applied across it this graph is curved so it is not an ohmic conductor diode because it has a high resistance with negative potential differences and a low resistance for positive potential differences. allow answers in terms of current tangent to the curve drawn at 2.3 V correct reading of Δy and Δx from graph either substitution of values into V = IR () value of R calculated () accept values in the range 0.50 to 0.65 Page 8 of 20

19 or calculation of gradient () allow ecf from incorrect readings of Δy and Δx calculation of R = / gradient () accept values in the range 0.50 to 0.65 [3] 5 (a) (i) 5.88 (watts) an answer of 5.9 scores 2 marks allow mark for correct substitution ie (ii) = allow mark for an answer of or allow 4 their (a)(i) correctly calculated 2 (b) (i) input power / energy would be (much) less (reducing cost of running) accept the converse electricity is insufficient (also) produce less waste energy / power accept heat for waste energy (as the waste energy / power) increases temperature of the cabinet so cooler on for less time (ii) line graph need to get both parts correct accept scattergram or scatter graph (c) both variables are continuous allow the data is continuous number of bulbs used-halogen=24 (LED=) total cost of LED = = accept a comparison of buying costs of halogen 36 and LED 30 Page 9 of 20

20 total cost of halogen= 24 x x 6.00 = 420 or buying cost of halogen is 36 and operating cost is 384 accept a comparison of operating costs of halogen 384 and LED allow for 3 marks the difference in total cost is if the number 24 has not been credited statement based on correct calculations that overall LED is cheaper must be both buying and operating costs an alternative way of answering is in terms of cost per hour: buying cost per hour for LED = p/ buying cost per hour for halogen = = 0.075p/ a calculation of both buying costs scores mark operating cost per hour for LED = = 0.4p/ operating cost per hour for halogen= = 0.8p/ a calculation of both operating costs scores mark all calculations show a correct unit all units correct scores mark statement based on correct calculations of both buying and operating costs, that overall LED is cheaper correct statement scores mark [2] Page 20 of 20