Readings Distance (m) Time (s) Velocity (m s -1 ) Force (N) 1 0,15 1 0,15 1,02 2 0,30 1,5 0,2 0,51 3 0,45 1,75 0,257 0,26 4 1,00 No effect 0 0

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1 Contextual questions 1 Two identical, light, graphite-coated balls, X and Y, both have a charge of C The balls are fixed to a horizontal, insulated X Y 5 cm surface The distance between the centres of X and Y is 5 cm C C 11 tate Coulomb s law in words 12 ketch the electric field pattern caused by X and Y You may assume that the surface does not affect the field 13 Calculate the electrostatic force (magnitude and direction) that X exerts on Y 2 learner reads that an electric field exists around a charged object, but that a noticeable force only acts in a restricted area around the object He decides to investigate this statement and plans it as follows: He charges two identical spheres and brings them into contact with each other He separates the spheres and places them on insulated stands far away from each other He measures accurate distances from each sphere, marks each distance and records it He places a small, very light ball that is easily charged, at the different marked distances and measures the time it takes to reach the sphere from each distance He also records the force that the ball experiences at each point He repeats the experiment with the second sphere and uses the average values to tabulate his results Readings Distance (m) Time (s) elocity (m s -1 ) Force (N) 1 0,15 1 0,15 1,02 2 0,30 1,5 0,2 0,51 3 0,45 1,75 0,257 0,26 4 1,00 No effect Give an investigative question for this investigation 22 What is a possible hypothesis for this investigation 23 Identify the dependent and independent variables of this investigation 24 Why is it necessary for the two spheres to make contact 25 Draw a graph with distance on the x-axis and force on the y-axis using the values in the table 26 What can you deduce, from your graph, about the relationship between the force and the distance between the objects 27 Was it necessary to determine the velocity of the ball Give a reason for your answer 28 Do you think that the information that the learner collected, is correct Explain your answer by referring to the results 29 What must be done with the results to obtain a graph that supports Coulomb s law Doc cientia technical sciences exercise book - Grade 11 45

2 3 The electric field strength at point X, 50 mm away from a positively charged, spherical particle P, is 10 N C What does the statement above mean 32 Draw a diagram to illustrate the electric field around particle P 33 Calculate the magnitude of the force that a charged particle Q, with charge +5 µc, will experience at point X ssume that all charges are stationary 34 Is this force toward or away from P Give a reason for your answer 4 Three charged spheres (-6 µc), B (-3 µc) and C (-1,5 µc) are placed as in the diagram with B at 0,04 m east of, and C at 0,03 m south of 41 Calculate the force of B on 42 Calculate the force of C on 43 Determine the magnitude and direction of the net force on due to the two forces 5 Two oppositely charged spheres are close to each other 51 ketch the electric field between the two spheres 52 Give three properties of electric field lines -6 μc 6 Peter charges a polystyrene ball so that it has an excess of 500 electrons 61 What type of charge does the ball have 62 Calculate the magnitude of the electric field 5 mm away from the ball, if the charge on the ball is C C 0,03 m C 0,04 m -3 μc B -1,5 μc 7 The diagram shows a small metal sphere, P, on an insulated stand P has a charge of C Draw the electric field pattern around P ssume that no other charges influence this pattern P 8 Two metal spheres with charges of C and C respectively, are placed 10 cm from each other as indicated in the diagram 10 cm C P C T 81 Calculate the magnitude of the electrostatic force that P exerts on T The spheres touch each other and are then returned to their original positions 82 Calculate the electric field strength of charge P at a distance of 10 cm 46 technical sciences exercise book - Grade 11 Doc cientia

3 9 X and Y are identical polystyrene balls, each with a mass of 15 g and the same positive charge They are placed in the container so that X is hovering in equilibrium above Y The distance between the centres of the balls is 20 cm 91 Explain why X stays in the air, by referring to the two forces acting on it 92 Calculate the gravitational force on X 93 tate Coulomb s law in words 94 Calculate the charge on each ball in coulombs X 20 cm 10 Two charged particles, Q 1 = +q and Q 2 = -q, are placed at a certain distance from each other If the following changes are made to the charges, what effect will it have on the magnitude and direction of the electrostatic force between them and the net electric field at point Z respectively The charged particles return to their original position before each following change Y Q 1 Q 2 Z Complete the following table: Change Net electrostatic force Net electric field Q 1 = +q Q 2 = -q Magnitude = F ttraction Magnitude: 2E -q +q +2q +2q -q -q +2q +½q Direction: from Q 1 to Q 2 11 Two charged particles, Q 1 = -q and Q 2 = +3q, are placed 5 cm from each other t point Z, distance x from Q 2 the net electric field is zero Calculate x Q 1 Z x Q 2 12 tudy the accompanying diagram that represents three charges on a plane and B are identical with charges of C each and are placed respectively north and east of C, which has a charge of C The distances between the charges are 6 cm and 12 cm as indicated in the diagram: Q = C 6 cm Q C = C 12 cm Q B = C Doc cientia technical sciences exercise book - Grade 11 47

4 121 tate Coulomb s law in words 122 Draw the electric field pattern that exists around the single negative point charge before any 2 positive charges are placed around it 123 Calculate the electrostatic force that B exerts on C 124 Determine the electrostatic force that exerts on C 125 Calculate the net electrostatic force that C experiences 126 Calculate the strength of the electric field of charge at a distance of 20 cm east of 13 The diagram shows a small metal sphere P on an insulated stand The sphere carries a charge of C, as indicated in the diagram: 131 Draw the electric field pattern around sphere P ssume that no other charges influence this pattern C P second metal sphere T, which carries a charge of C, is placed 1 cm from sphere P, as shown in the diagram below: 1 cm C P T C 132 Calculate the magnitude of the electrostatic force that sphere P exerts on sphere T 14 tudy the following diagram of the front part of a spark plug The electric field strength between the electrodes of the spark plug is 2, N C -1 just before the spark plug fires The gap between the electrodes is 0,3 mm gap between the electrodes 141 Calculate the electrostatic force exerted on an electron to accelerate it from one electrode to the other You can use a charge of qe = 1, C for the electron 142 Calculate the potential difference between the electrodes just before the spark plug fires 48 technical sciences exercise book - Grade 11 Doc cientia

5 15 potential difference of is set up across two parallel plates that are 25 mm apart particle, Q, with a charge of -4, N C -1, is placed at the negative plate before it is released 151 Find the strength and direction of the electric field between the plates 152 Calculate the electrostatic force exerted on charge Q Q 16 The four light bulbs in the diagram have the same resistance Calculate the emf of the battery if the ammeter reading is 2 and the voltmeter reading is 3 ssume that the resistance of the connecting wires, the battery and the ammeter are negligible and that the resistance of the voltmeter is very large There is no internal resistance in the battery B 1 B 2 Calculate the emf of the battery how all calculations B 3 B 4 17 battery with negligible internal resistance, is connected in a circuit as shown 171 how by means of calculations that the effective external resistance is 3,2 Ω, with closed 172 When switch is closed, the ammeter reading is 6 Calculate the readings on: 1721 voltmeter voltmeter witch is now opened Without any calculations, state whether the readings on the following will INCREE, DECREE or REMIN CONTNT: 1731 oltmeter oltmeter mmeter 1 4 Ω 10 Ω 6 Ω 2 Doc cientia technical sciences exercise book - Grade 11 49

6 18 In the circuit diagram the battery has negligible resistance and an emf of 15 Resistors R 1, R 2 and R 3 are 4 Ω, 6 Ω and 3 Ω respectively 181 Calculate the effective resistance of the parallel resistors, with 1 closed 182 If only switch 1 is closed, 3 has a reading of 7,5 Calculate the current in the circuit (reading on ammeter ) 183 If switch 2 is now also closed, indicate whether the following INCREE NOTICEBLY, DECREE NOTICEBLY or REMIN CONTNT: 1831 oltmeter reading mmeter reading 1 2 R 3 = 3 Ω 3 1 R 1 = 4 Ω R 2 = 6 Ω 2 19 In the circuit diagram, bulb L has a resistance of 43 Ω and the internal resistance of the battery is negligible The voltmeter reading when switch is closed is 52,2 191 Calculate the effective resistance of the parallel resistors 192 Calculate the: 1921 current through the battery when switch is closed; 1922 emf of the battery; 1923 the reading on the ammeter when switch is closed L 30 Ω 30 Ω 20 In the circuit diagram, the battery has an emf of 10 and negligible internal resistance oltmeter 1 is connected across the battery and voltmeter 2 across the open switch The resistance of the connecting wires and the ammeter can be ignored With switch open: 201 what is the reading on what is the reading on What is the reading on 2 with switch closed 204 Calculate the reading on the ammeter with switch closed 1 Ω Ω 3 Ω 50 technical sciences exercise book - Grade 11 Doc cientia

7 21 The graph below shows the results of an experiment in which current flows through a light bulb, while a voltmeter measures the potential difference across the terminals of the light bulb current () 0,4 0,35 0,3 0,25 0,2 0,15 0,1 0, potential difference () 211 What is the potential difference when the current is 0,2 212 What is the resistance of the light bulb when the current is 0,2 213 Does the resistance of the light bulb change with an increase in current Confirm your answer by referring to the graph 214 tate Ohm s law in words 22 circuit is set up by learners as in the diagram below: Calculate the reading on the ammeter if the battery has an emf of 6 and negligible internal resistance and all four of the resistors are identical, with a resistance of 1 Ω 23 Three cells, each with emf = 3 and resistance are connected in series in a circuit as shown in the diagram below 231 What is the voltmeter reading when both switches are open Both switches, 1 and 2, are now closed 232 Calculate the reading on ammeter Calculate the reading on the voltmeter 234 Calculate the reading on ammeter 2 2,5 Ω Ω 3 Ω C B 2 3 Ω Doc cientia technical sciences exercise book - Grade 11 51

8 24 The circuit diagram represents a combination of resistors in series and parallel The battery has an emf of 12 and negligible internal resistance Ɛ = 12 With switch OPEN, ammeter reading = 1,2 241 Calculate the total resistance of the circuit, with switch open 242 Calculate the potential difference across the 3,6 Ω resistor 8 Ω R 3,6 Ω witch is now CLOED 243 How will each of the following be affected Only state INCREE, DECREE or REMIN CONTNT 2431 The total resistance of the circuit 2432 The reading on ammeter 25 Thembi constructs circuit, as shown in the diagram, and takes readings on the ammeter and voltmeters If she then decreases the resistance of the rheostat considerably, will the following decrease, increase or stay the same 3,6 Ω 2511 The reading on 1 8 Ω 2512 The reading on The sum of the readings on Give a reason for your answer to Question In the circuit, the identical cells each have an emf of 3 and negligible internal resistance The voltmeters have very high resistances and the resistance of the ammeter need not be considered 261 witch is open What are the readings on: 2611 voltmeter voltmeter witch is now closed What are the readings on: 2621 the ammeter 2622 voltmeter 2 3 Ω 6 Ω 1 Ω 2 27 The battery, emf = 60, has no internal resistance in this circuit The potential difference across R 1 is 15 and the current through the ammeter is 3 when switch is closed The resistance of R 2 is three times that of R 1 R 1 R 2 52 technical sciences exercise book - Grade 11 Doc cientia