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GAUTENG DEPARTMENT OF EDUCATION SENIOR SECONDARY INTERVENTION PROGRAMME PHYSICAL SCIENCES GRADE 10 SESSION 16 (LEARNER NOTES) CONSOLIDATION – MAGNETISM, ELECTROSTATICS & ELECTRICITY Learner Note: Focus on the topics in this section. It forms the foundation of grade 11 work on magnetism, electrostatics and electricity SECTION A: TYPICAL EXAM QUESTIONS Question 1: 10 minutes (Adapted from GDEJune 2009) (This is a different way of showing the forces between magnets. Remember a spring balance is used to measure force – do not be put off because you have never seen the diagram. Any setup can be asked, the theory stays the same, just the examples vary) Learner Note: It is important to understand what is meant by each of the 3 types of variables – this must be included in various sections of the write up or questions on investigations. It must be answered correctly – vague answers will not earn any marks. Practise these regularly! A learner conducted an investigation as shown below Magnet X Magnet Y Spring balance (N) Distance N S N Masking tape The learner investigates the force of attraction between two magnets X and Y. X is taped down to prevent it from moving. Y is placed at different distances from X and the force readings at each distance are recorded by using the spring balance. 1.1 Write an investigative question for the experiment (2) (An investigative question must state …What is the relationship between dependent and independent variable. Be specific, mention a constant variable and don’t forget to use a question mark! Mostly the description of the investigative question can be converted to a question) 1.2 Name the dependant variable in the investigation (What do you test?) (1) Page 1 of 6 GAUTENG DEPARTMENT OF EDUCATION SENIOR SECONDARY INTERVENTION PROGRAMME PHYSICAL SCIENCES GRADE 10 SESSION 16 (LEARNER NOTES) 1.3 Name the independent variable in the investigation (1) (What do you change and what change do you make? ie. increase / decrease) 1.4 Name two constant variables (Full sentences!) (2) 1.5 Write a hypothesis for the investigation (3) (9) Question 2: 5 minutes (Taken from MED Nov 2009) Learner Note: Understand the terminology in this section – the domain theory is important, illustrate it by means of a diagram. Once understood it will be easy to remember. Know the ferromagnetic substances. Co, Ni, Fe. Paper clips are attaches to thin thread and fixed to the surface as shown. The paper clips are made of steel. The paperclips are suspended as shown when the magnet is brought near. N A S B 2.1 2.2 What is a ferromagnetic substance? Identify the pole that is induced at the top of paper clip A (Remember the principle of attraction between different poles) (2) (1) 2.3 Use the domain theory to explain how the paper clip becomes magnetised (Steel is an alloy of iron and is a ferromagnetic substance) (4) (7) Question 3: 5 minutes Learner Note: It is common that the terms electric field and magnetic field are confused and used incorrectly in an exam. Remember charged particles have electric fields – they are charged when electrical charges are transferred. Magnets have magnetic fields). 3.1 3.2 Predict what will happen when two positively charged polystyrene spheres move close together. (2) (Law of attraction and repulsion between charges) Predict the effect of an increased charge on one of the spheres on the electrostatic force between them (2) Page 2 of 6 GAUTENG DEPARTMENT OF EDUCATION SENIOR SECONDARY INTERVENTION PROGRAMME PHYSICAL SCIENCES GRADE 10 SESSION 16 (LEARNER NOTES) (Remember when the charge is greater, the field is stronger … What is the definition of the field?) 3.3 3.4 The charged spheres are brought close together, what is the effect on the electrostatic force between them? (2) If one sphere loses its charge, will it be attracted to the other? Explain (2) (Refer to Law of attraction and repulsion! This one is commonly answered incorrectly.) (8) Learner Note: Neutral objects are attracted by charged objects due to electric polarisation Question 4: 10 minutes (Adapted from Study and Master Grade 10) Give one term for the following statements Learner Note: Focus on the topics in this section. It forms the foundation of grade 11 work on magnetism, electrostatics and electricity (Memorize the terms! The one word answers are either definitions or are derived from equations – Make sure you refer to your formulae on the information sheet when you deal with questions eg. 4.5 Do not guess answers. Know your formulae, what each symbol represents an the unit of each quantity). 4.1 The electrical energy converted to light in a bulb per unit charge (1) 4.2 Lines around a magnet showing force exerted (1) 4.3 The area where a charged object exerts a force (1) 4.4 The process causing a charged object to attract an uncharged object (1) 4.5 The amount of charge passing a point in a conductor in a period of time (1) 4.6 An object that contains more protons than electrons (1) 4.7 The charge obtained by glass and Perspex when rubbed (1) 4.8 The charge on PVC, amber and polythene when rubbed (1) 4.9 The total amount of electrical energy that a cell can supply (1) 4.10 An object that can experience a force on an electric field (1) (10) Page 3 of 6 GAUTENG DEPARTMENT OF EDUCATION SENIOR SECONDARY INTERVENTION PROGRAMME PHYSICAL SCIENCES GRADE 10 SESSION 16 (LEARNER NOTES) SECTION B: SOLUTIONS AND HINTS Question 1 1.1 What is the relationship between the distance between the opposite magnetic poles and the force of attraction between the magnets? (Two marks or none are allocated, take note of criteria for full marks) 1.2 The force of attraction between the magnets 1.3 The distance between the opposite magnetic poles is changed (Full sentences! You cannot just say distance! What is done to the distance?) 1.4 The same magnets must be used The same spring balance must be used 1.5 If magnets are brought closer to one another with opposite poles facing, the force of attraction will increase as the magnetic field becomes stronger the closer you get to the poles (Be specific! Use correct terms) Question 2 2.1 2.2 2.3 Materials that can be magnetised and then retain their magnetism South When the ferromagnetic material is placed in the magnetic field the domains of the material will become aligned with the magnetic field lines of the magnet. The paper clip is then magnetised (One mark per fact! Check mark allocation) Question 3 3.1 3.2 3.3 3.4 Opposite charges repel, the sphere will be pushed away An increase in charge will increase the repulsive force, a greater charge causes a greater field The electrostatic force is increased, the field is stronger closer to the charge. Will still attract, positively charged objects polarise the neutral object to cause two opposite ends. Page 4 of 6 GAUTENG DEPARTMENT OF EDUCATION SENIOR SECONDARY INTERVENTION PROGRAMME PHYSICAL SCIENCES GRADE 10 SESSION 16 (LEARNER NOTES) Question 4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 Potential difference Magnetic field lines Electric field Polarisation Current Positive Positive Negative emf Electrically charged object (Terms may have more than one word ie. 4,2; but is still not a sentence) SECTION C: ADDITIONAL CONTENT NOTES Refer to Notes in Sessions 12 - 15 SECTION D: HOMEWORK Question 1: 20 minutes Study the diagram below. The resistors are identical. V1 3 cells in series A4 A1 V3 V2 A2 A3 V4 1.1 Compare the voltmeter readings, give reasons for your answers (10) 1.2 Compare the ammeter readings, give reasons (10) Learner Note: It is more difficult to do questions where no calculations are involved. It requires a thorough understanding of the rules in this section. Page 5 of 6 GAUTENG DEPARTMENT OF EDUCATION SENIOR SECONDARY INTERVENTION PROGRAMME PHYSICAL SCIENCES GRADE 10 SESSION 16 (LEARNER NOTES) SECTION E: SOLUTION SESSION 15 HOMEWORK Question 1 1.1 4,5 V 1.2 R= 5= = 1,8 x 0,9 x 3 = 48,6 J V I 4,5 I 1.4 1 1 1 Rp 2 3 I = 0,9 A R= V I 2= V 0,9 1 1 1 R p R1 R 2 1 3 2 Rp 6 6 Rp = V2 = 1,8 V Rp = 1,2 Emf = V2 + V3 4,5 = 1,8 + V3 V3 = 2,7 V 1.3 W = VIt 6 5 1.5 R= V I 1,2 = 4,5 I I = 3,75 A 1.6 What is the relationship between the resistance and the current in the circuit if the bulbs are connected in series and parallel respectively? 1.7 When the bulbs are connected in series the resistance increases and the current in the circuit decreases. When the resistors are connected in parallel, the total resistance decreases and the current in the circuit increases, the bulbs in parallel are current dividers The SSIP is supported by Page 6 of 6