Contents Preface iii Part One Tips for Scoring Higher Tips for Scoring Higher 3 Three advices Signs and directions Big picture Part Two Topic-based Exercises E1. Charge, E-field and Potential 11 Remember me Ensure you know these Multiple-choice questions Short questions Long questions Shoot-the-stars questions E. Electric Circuit 7 E3. B-field and Electromagnet 41 E4. Moving Charges in B-field 51 E5. Electromagnetic Induction 69 E6..c. Transmission and Mains 89 Part Three Revision Exercises E7. Skill-sharpening Exercises 17. From-a-graph B. Which-graph C. Explain-a-phenomenon D. Describe-a-method E. Design-a-circuit E8. Integrated Exercises 11 Dessert: Selected Overseas Questions 15 ppendices. Intensive Basic Training 131 1. Converting units. Changing subjects and solving equations 3. Drawing circuit diagrams 4. Calculating equivalent resistance 5. Determining directions of F, B and I 6. Sense of dependence B. Rough Idea of Your Level 145 C. Useful Formulas and Constants 146 i
Tips for Scoring Higher Practice makes perfect, only if you are on the right track. Tip s: Th re e adv i ce s H ow to rea d a qu es ti on Why my answer looks so strange Big picture Tips for Scoring Higher Three advices 1. Highlight the keywords and data Use a highlight pen when reading questions. Don t miss the clues.. Let the equations guide your thinking Concentrate on the variables and their relations. Don t just put the numerical values into the equations. The Remember me section in each topic helps. 3. Read the solution guide even if you get the right answers. If so, you will learn much more. Have you read the Preface? 3
Electric Circuit Unit E Shoot-the-stars questions Reason-assertion 1st statement 1. Thick wires are used for circuits involving large currents.. The more identical bulbs connected in parallel with a practical cell with some internal resistance, the dimmer the bulbs. 3. heating element of a higher power has thicker wires. nd statement Thick wires have small resistance. The more identical bulbs connected in parallel with a practical cell, the smaller the current drawn from the cell. By P = I R, the larger the resistance, the higher the power for the same current. Reminder:. = T T and (1 because of ) B. = T T C. = T F D. = F T See p.1 for detailed directions. Think and solve 4. Two cells and two resistors are connected as shown. Neglect the internal resistance of the cells. What are (a) the p.d. across C and (b) the current through C? (a) (b). V m B. 4 V m C. V.5 m D. 4 V.5 m V B 4 V 4 kω D C kω 6. semiconductor is connected across a 9 V battery. Which of the following graphs best shows the change of current I that the battery delivers as a function of temperature?. I B. I temperature C. I D. I temperature Electric Circuit 5. Six identical resistors are connected as shown in the figure. Between which two points is the equivalent resistance the max.? X. X and Y B. X and Z C. Y and Z D. ll are equal. Z Y temperature 7. Four resistors are connected to a cell as shown. If a 1 Ω resistor is connected across B, what will be the current flowing through it?. zero B..67 C. 1.3 D. temperature Ω 4 Ω 3 Ω B 6 Ω 1 V ns: 1.. C 3. B 4. C 5. 6. D 7. 39
Unit E Electric Circuit 8. Three unknown 9 V devices X, Y and Z are I connected in a circuit as shown. It is found X Y Z that X and Y dissipate 1 W and 8 W 1 Ω respectively, while Z supplies 4 W to the circuit. If the battery can provide a max. power of 36 W, what is the current I in the main loop?. 1 B. C..5 D. 4 9. rheostat r and a 1 Ω resistor are in parallel with 1 a power supply across them. The current from the supply is always kept 1 Ω r constant at 1. The rheostat r is adjusted to maximize the power P dissipated by r. What is the max. P?. 15 W B. 5 W C. 5 W D. 1 W wire length cross-sectional area X 64 cm.3 mm Y 3 cm 4.6 mm. 1.4 V B..4 V C. 3.5 V D. 6.6 V 11. (Very challenging) right-angle triangular plate is as shown and B = BD = BC. The resistance across C is r. What is the resistance across BD?..5r B..5r C. r D. r 1. (Very challenging) cubic D frame has 1 identical edges. B Each edge has the same H resistance r. Find the equivalent resistance R across E F (a) cube diagonal G and (b) face diagonal F. B C C G D Electric Circuit 1. Paul has two resistance wires X and Y made of the same material. He attaches one end of X to an end of Y to form a longer wire. If the free end of X is set at a potential of 8 V, and the free end of Y at 1 V, what is the potential at the junction of the two wires approximately? (Hint: Note the equipotential points. They can be shorted without affecting the circuit.) (6 marks) 4 ns: 8. C 9. B 1. B 11. 1a. 5r/6 1b. 3r/4
E7 Skill-sharpening Exercises Unless otherwise specified, take e = 1.6 1 19 C, ε = 8.85 1 1 C N 1 m and μ = 4π 1 7 T m 1. Categories: Fro m-a - gra ph Whi c h- gra ph Ex p l ai n- a- p he n ome n on Describe-a-method D e si gn- a- ci rcu it. From-a-graph 1. point charge q is solely under the influence of an elec. field around another charge Q. The graph below shows how its acceleration a varies with time t. Which of the following statements MUST be correct? (1) The elec. force on q decreases with time. () q is moving away from Q. (3) q is positive.. (1) only B. () only C. (1) and () only D. (1), () and (3) a t. mobile phone uses a battery X that is capable of delivering a constant current of 8 m for 5 hours. The graph of current against time for another battery Y is as shown. What is the charge delivered by this battery? I / m 8. the same as that by X B. greater than that by X C. less than that by X D. cannot be determined 3. The voltage-current relation of an elec. component is shown. Which of the following statement(s) is/are correct? (1) Resistance at P is 4.5 Ω. () The resistance of the component decreases with increasing I. (3) The component may be a tungsten wire.. () only B. (3) only C. (1) and () only D. (1) and (3) only 9 V / V 4 6 P t / h I / Skill-sharpening Exercises ns: 1. C.. C 3. C 17
Unit E7 Skill-sharpening Exercises 4. Three resistors, R 1, R and R 3 are connected to an ideal cell. The variation of potential and current along path BC is shown below. ϕ / V 3 1.5 I / B R 1 C R 3.5 R B C B C Find the resistance of R and R 3. ssume the wires have no resistance. R R 3. Ω 1.33 Ω B. 1 Ω 1.33 Ω C. Ω.67 Ω D. 1 Ω.67 Ω 5. The graph shows the output e.m.f. of a simple generator. Which of the following statements are correct? e.m.f. output (1) The generator consists of a commutator, instead of slip rings. () The no. of magn. field lines through the generator coil is max. at t = t 1. (3) The curve becomes negative (turns upside down) if the generator coil is rotated in the opposite direction. t 1 t. (1) and () only B. (1) and (3) only C. () and (3) only D. (1), () and (3) 6. In a transformer, the primary and secondary voltages have the relation with time as shown. 15 1 V V s What is the turns ratio N p : N s?. 3 : 1 B. 15 : 1 C. 1 :.667 D. : 3 V p t (For full-x physics only) Skill-sharpening Exercises 7. wire loop is placed in a uniform magn. field. Which of the following will give an induced current as shown? (1) The magn. field changes at an increasing rate. () The area enclosed by the coil shrinks at a constant rate. (3) The coil rotates about XY. X Y I induced t. (1) only B. () only C. (1) and () only D. () and (3) only 18 ns: 4. B 5. D 6. D 7.
ppendix Intensive Basic Training Exercise 5 (3 min) 1. Which of the following is a possible unit of electric field?. N m 1 B. V m 1 C. C N 1 D. N C. Which of the following is the correct unit of the electric constant ε?. C 1 N m B. C N 1 m C. C N m 1 D. C N 1 m 1 3. Which of the following is a possible unit of electric charge?. m h B. N C C. V m 1 D. s 1 4. Which of the following is a quantity of electric force? Given β = 9 1 3 N m μc. 1 3 µ C. β cm B. β 3 µ C cm C. 1 3 µ C β cm (Q5 6: physics only) D. β 3 µ C cm 5. Which of the following is a quantity of magnetic field?. 1 N µ B. ( 1m) 4π ( m) C. 1 N µ D. 1m π m ( ) 6. Which of the following is a quantity of energy?. 3 1 8 m s 1 3 1 3 kg 3 1 8 m s B..1 N m C. 3 1 8 m s 1 3 1 3 kg 3 1 8 m s 1 D. 5 V 8 C / 1 s Exercise 6 (3 min) 1. Which of the following is a possible unit of voltage?. N m 1 B. V m 1 C. Ω 1 1 1 D. W Ω. Which of the following is a possible unit of power?. V Ω B. V Ω 1 C. Ω D. Ω 1 3. Which of the following is a possible unit of resistance?. W V 1 B. mv C. kw m D. T m 4. Which of the following is a quantity of work done by electric force on a charge?. m 8 C m ( 8 C) B. 4πµ ( 1m) 4πε ( 1m) C. m 8 C D. 4πε 1C 4πε 1 m ( ) (Q5 6: physics only) 5. Which of the following may be a quantity of induced e.m.f. by a magnetic field?. 5 Hz m 1 π 8 T B. (8 T).5 m 3.5 m s 1 C..5 m 5 C 3.5 m s 1 D. 8 T m / (. s) 6. Which of the following is a quantity of mass?. 931.5 MeV B. 931.5 ev / (3 1 8 m s 1 ) C. 931.5 MeV / (3 1 8 m s ) D. 1.49 1 1 J / (3 1 1 cm s 1 ) 13 ns: (Ex 5) 1. B. B 3. 4. D 5. C 6. C (Ex 6) 1. D. B 3. C 4. B 5. 6. D
Intensive Basic Training ppendix 3 Drawing circuit diagrams Draw circuit diagrams to represent the following circuits. 1. battery box switch bulb bulb. battery box switch voltmeter bulb 3. battery box R bulb ammeter 4. battery box ammeter R voltmeter ns: 1.. 3. 4. V V 135