Catholic High 2022 Year 4 Physics TA3 with ANSWERS (FINAL)

Name: ANSWERS Index Number: Class: CATHOLIC HIGH SCHOOL Term 3 Class Test Year 4 (Integrated Programme) PHYSICS Moments, Energy, Work and Power, Current of Electricity, DC Circuits, Practical Electricity, Magnetism, Electromagnetism, Electromagnetic Induction 11 Aug 2022 40 minutes READ THESE INSTRUCTIONS FIRST Write your name, index number and class on all the work that you hand in. Write in dark blue or black pen. Do not use paper clips, glue or correction fluid. The use of an approved scientific calculator is expected, where appropriate. At the end of the examination, fasten all your work securely together. Section A: Multiple Choice There are ten questions in this section. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in the table provided at the end of this section. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. Section B: Structured You may use an HB pencil for any diagrams or graphs. Answer all questions. Candidates are reminded that all quantitative answers should include appropriate units. Candidates are advised to show all their workings in a clear and orderly manner, as more marks are awarded for sound use of Physics than for correct answers. The number of marks is given in brackets [ ] at the end of each question or part question. For examiner’s use only: Section A / 10 Section B / 25 formula s.f.   Total / 35 This document consists of 11 printed pages.

2 Section A Answer all the questions in this section. Record your choice in the table below. Answers for Section A 1 2 3 4 5 6 7 8 9 10 1 A student would like to conduct a plumb line experiment to determine the centre of gravity of a cardboard. Which of the following steps is not needed in determining the cardboard’s centre of gravity? A ensuring that the cardboard can oscillate freely. B hanging a plumb line from the pivot. C pivoting the cardboard near its centre of gravity. D tracing the plumb line on the cardboard. 2 The figure below shows a drop slide where the first part of the fall is vertical. A child of mass 30 kg uses the drop slide, slides down to C and then stops at D. The child is initially at rest at A. Assuming there is no friction acting on the child during his fall from A to C, what is the average frictional force acting on the child as he slides between C and D? A 37 N B 140 N C 370 N D 740 N 3 A power station provides 2.0 MW of total power and produces 900 kW of wasted energy in its operations. What is the useful electrical energy produced by t he power station in two hours? A 1.8 MWh B 2.2 MWh C 132 MWh D 7920 MWh

3 4 A wire has a resistance of 10 Ω. A second wire, made of the same material, has 4 times the length and twice the diameter. What is the resistance of the second wire? A 2.5 Ω B 10 Ω C 20 Ω D 40 Ω 5 Five identical resistors of resistance 3 Ω each are arranged as shown. Given that the potential difference between points P and R is 1.0 V, which values are correct? effective resistance between P and R / Ω potential difference between Q and S / V A 0.67 0.0 B 0.67 0.5 C 1.50 0.0 D 1.50 0.5 6 The diagram shows a variable potential divider connected to a power supply and a lamp. What happens to the brightness of the lamp and the potential difference across PS as the sliding contact S moves from P to Q? brightness of lamp potential difference across PS A brighter decreases B brighter increases C dimmer decreases D dimmer increases P Q R S

4 7 An electrical cable contains three wires: live, neutral and earth. The cable is correctly wired to a plug which contains a 3 A fuse at the live wire. The insulation becomes damaged and the wires are exposed. Which event causes a short circuit and the fuse to blow? A A person touches the earth wire. B A person touches the live wire. C A person touches the neutral wire. D The live wire touches the earth wire. 8 The steps to demagnetise a magnet using electrical method are shown below. 1. Connect a solenoid to _______________ supply. 2. Place the magnet into the solenoid and switch on the circuit. 3. Slowly withdraw the magnet in the _______________ direction until it is far away from the solenoid. Which of the following options in step 1 and 3 is correct? blank in step 1 blank in step 3 A alternating current east-west B alternating current north-south C direct current east-west D direct current north-south 9 The diagram shows a beam of electrons entering a magnetic field. The direction of the field is out of the page. What is the initial direction of the deflection of the electrons as the beam passes through the electric field? A into the page B out of the page C towards the bottom of the page D towards the top of the page

5 10 The diagram shows a transformer. A 12 V, 24 W lamp is connected to the output of the secondary coil. Given that the input source is 24 V, which setting allows for the lamp to operate at normal brightness? ratio of Ns / Np current in primary coil / A A 0.5 1.0 B 0.5 2.0 C 2.0 1.0 D 2.0 2.0

6 Section B Answer all the questions in this section. 11 Fig 11.1 shows a lighting circuit of a house. All the bulbs in the circuit are labelled “240 V, 60 W”. Fig. 11.1 (a) Describe what is meant by “240 V, 60 W”. It means that when a potential difference of 240 V is applied across the bulb, it will convert 60 J of electrical energy to light and thermal energy per second. [1] (b) State and explain what happens to the brightness of the other light bulbs if one bulb blows. The brightness of the other light bulbs will remain the same [B1] as the potential difference/current across them remains the same [B1]. [2] (c) Determine a suitable rating of a fuse at position Z. I = P / V = 60 / 240 = 0.25 A [B1] Main current = 3I = 0.75 A Suitable rating = 1 A [B1] fuse rating = [2] Z

7 12 Fig. 12.1 shows the current -potential difference (p.d) graphs for a resistor and a thermistor. Fig. 12.1 (a) Calculate the resistance of the thermistor when the potential difference across it is 7.0 V. From graph, current = 4.6 A R = V / I = 7.0 / 4.6 [M1] = 1.52 Ω [A1] resistance = [2] (b) The potential difference across the thermistor and resistor is increased from 0 V to 7.0 V. State the effect of this on their respective resistances. effect on resistance Thermistor Decreases Resistor Same/No change [2] (c) The thermistor and resistor are connected in parallel to a 7.0 V supply. Calculate the current from the supply. From the graph, I = 4.6 A [B1, allow ecf from part a] Current from supply = I + I = 4.6 + 4.6 = 9.2 A [A1]

8 current = [2] 13 Fig. 13.1 shows a U-shaped electromagnet. Fig. 13.1 (a) Determine the polarities of X and Y. polarity X South Y South [1] (b) Without changing the magnet, suggest one way to increase the magnetic field strength of the electromagnet. Increase magnitude of current by increasing emf OR Increase number of turns of coil per unit length [B1] [1] X Y

9 14 Fig.