CLASS TEST GRADE 11 PHYSICAL SCIENCES: PHYSICS Test 3: Electricity and magnetism MARKS: 45 TIME: 1 hour INSTRUCTIONS AND INFORMATION 1. Answer ALL the questions. 2. You may use non-programmable calculators. 3. You may use appropriate mathematical instruments. 4. Number the answers correctly according to the numbering system used in this question paper. 5. Data sheets are attached for your use. 6. Wherever motivation, discussion, et cetera is required, write brief answers.
SECTION A QUESTION 1: ONE-WORD ANSWERS Give ONE word or term for EACH of the following descriptions. Write only the word or term next to the question number (1.1 1.2). 1.1 Charge stored per volt. (1) 1.2 An electrical device that can increase the input voltage. (1) [2] QUESTION 2: FALSE STATEMENTS Correct the following FALSE statements. Write the correct statement next to the question number (2.1 2.2). 2.1 Current in an electric circuit is directly proportional to the resistance, provided the temperature changes. (2) 2.2 When two resistors are in parallel, their combined effective resistance is equal to the resistance of the smaller resistor. (2) [4] QUESTION 3: MULTIPLE-CHOICE QUESTIONS Choose the correct answer to the following questions. Write only the letter (A D) next to the question number (3.1 3.2). 3.1 Which one of the following will decrease the electric field strength between oppositely charged parallel plates? A Increasing the potential difference between the plates B Decreasing the thickness of the plates C Increasing the distance between the plates D Bringing the plates closer to each other (2) Maskew Miller Longman, Focus on Physical Sciences Grade 11 Test 3: Electricity and magnetism Page 2 of 7
3.2 Consider the circuit below. Which of the voltmeters will have the same reading? A V1, V2, V3 B V1 and V2 C V1 and V3 D V2 and V3 (2) [4] TOTAL SECTION A: 10 Maskew Miller Longman, Focus on Physical Sciences Grade 11 Test 3: Electricity and magnetism Page 3 of 7
SECTION B INSTRUCTIONS AND INFORMATION 1. The formulae and substitutions must be shown in ALL calculations. 2. Round off your answers to TWO decimal places where applicable. QUESTION 4 Two uncharged metal spheres, P and Q, on insulated stands are placed next to each other as shown below. A negatively charged sphere X is placed next to P. 4.1 Draw the charge distribution in P and Q. (2) Sphere X, carrying a charge of 2 10 6 C, is brought to touch sphere P and then placed a distance of 3 cm from P. 4.2 State the law that will help you calculate the force between X and P. (3) 4.3 Calculate the force exerted by the spheres X and P on each other. (4) 4.4 How many excess electrons does sphere P have? (3) [12] QUESTION 5 A 2,5 µf capacitor is connected to a 12 V battery. After a short while the potential difference across the capacitor is 12 V. 5.1 Calculate the charge stored in the capacitor. (3) 5.2 If the area of the plates is 7,5 10 5 m 2, calculate the distance between the plates. (4) 5.3 How does a dielectric increase the capacitance of a capacitor? (2) [9] Maskew Miller Longman, Focus on Physical Sciences Grade 11 Test 3: Electricity and magnetism Page 4 of 7
QUESTION 6 A transformer with negligible power loss is connected to a 120 V input, and the secondary feeds into a load of 2,8 10 5 Ω. The windings have 600 turns in the primary and 15 000 in the secondary. 6.1 On what principle does a transformer function? (1) 6.2 Calculate the output potential difference. (4) [5] QUESTION 7 7.1 Consider these conductors: light bulb; nichrome wire. 7.1.1 Which one is a non-ohmic conductor? (1) 7.1.2 How does a non-ohmic conductor differ from an ohmic conductor? (2) 7.2 A battery with an emf of 12 V is connected in series with an ammeter, a switch (S) and a 4 Ω resistor. A 2 Ω resistor is connected in parallel with the 4 Ω resistor. When switch S is closed, a voltmeter across the battery reads 9 V. 7.2.1 Why is there a decrease in the voltmeter reading when the switch is closed? (1) 7.2.2 Calculate the internal resistance of the battery. (5) [9] TOTAL SECTION B: 35 GRAND TOTAL: 45 Maskew Miller Longman, Focus on Physical Sciences Grade 11 Test 3: Electricity and magnetism Page 5 of 7
DATA FOR PHYSICAL SCIENCES GRADE 11 PHYSICS PHYSICAL CONSTANTS NAME SYMBOL VALUE Acceleration due to gravity g 9,8 m s 2 Speed of light in a vacuum c 3,0 10 8 m s 1 Gravitational constant G 6,67 10 11 N m 2 kg 2 Coulomb s constant k 9,0 10 9 N m 2 C 2 Charge on electron e 1,6 10 19 C Electron mass m e 9,11 10 31 kg Permittivity of free space ε 0 8,85 10 12 F m 1 FORMULAE MOTION v f = v i + aδt v f 2 = v i 2 + 2aΔx Δx = v i Δt = 1 2 aδt2 Δx = ( v + v f i 2 ) Δt FORCE F net = ma p = mv F = Gm m 1 2 FΔt = Δp = mv mu r 2 μ s = f s(max) N μ = f k k N WEIGHT AND MECHANICAL ENERGY F g = mg U = E p = mgh K = E k = 1 2 mv2 Printed with permission, National Department of Education Maskew Miller Longman, Focus on Physical Sciences Grade 11 Test 3: Electricity and magnetism Page 6 of 7
WAVES, LIGHT AND SOUND v = f λ or v = v λ T = 1 f or T = 1 v ELECTROSTATICS F = kq Q 1 2 ( k = 9,0 10 r 2 9 N m 2 C-2 ) E = F q E = kq r 2 ( k = 9,0 10 9 N m 2 C -2 ) E = V d V = W Q W = QEs U = kq Q 1 2 r (k = 9,0 109 N m 2 C -2 ) C = Q V C = e 0 A d ELECTROMAGNETISM e = N ΔΦ Δt V s V = N s p N p Φ = BA F = qvb CURRENT ELECTRICITY I = Q Δt emf = I(R + r) R = V I R = r 1 + r 2 + r 3 + 1 R = 1 r + 1 1 r + 1 2 r + 3 Printed with permission, National Department of Education Maskew Miller Longman, Focus on Physical Sciences Grade 11 Test 3: Electricity and magnetism Page 7 of 7