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Name :________________________________ Handout Topic 5, 10-11 New Electromagnetism Review MULTIPLE CHOICE 1. 2. Which one of the following is a correct definition of electric potential difference between two points? A. The power to move a small positive charge between the two points. B. The work done to move a small positive charge between the two points. C. The power per unit charge to move a small positive charge between the two points. D. The work done per unit charge to move a small positive charge between the two points. Electric field strength is defined as A. the force exerted on a test charge. B. the force per unit positive charge. C. the force per unit charge. D. the force per unit charge exerted on a positive test charge. 1 3. Two identical spherical conductors X and Y are mounted on insulated stands. X carries a charge of +8.0 nC and Y carries a charge of –2.0 nC. –2.0nC +8.0nC conductor X insulated stands conductor Y The two conductors are brought into contact and are then separated. Which of the following gives the charge on each conductor? Charge on X Charge on Y A. 0.0 nC 0.0 nC B. +8.0 nC –2.0 nC C. +5.0 nC +5.0 nC D. +3.0 nC +3.0 nC 2 4. Two long, vertical wires X and Y carry currents in the same direction and pass through a horizontal sheet of card. X Y Iron filings are scattered on the card. Which one of the following diagrams best shows the pattern formed by the iron filings? (The dots show where the wires X and Y enter the card.) A. B. C. D. 3 5. In the circuit below, which meter is not correctly connected? A 1 3 V 2 A 4 V 6. A. 1 B. 2 C. 3 D. 4 The electron volt is defined as –19 A. a unit of energy exactly equal to 1.6 × 10 J. B. 1 a fraction 13.6 of the ionization energy of atomic hydrogen. C. the energy gained by an electron when it moves through a potential difference of 1.0 V. D. the energy transfer when 1.0 C of charge moves through a potential difference of 1.0 V. (1) 4 7. In the circuit below, n charge carriers pass the point P in a time t. Each charge carrier has charge q. P The current in the circuit is given by the expression 8. A. q t . B. nq t . C. qt n . D. nqt. The element of an electric heater has a resistance R when in operation. What is the resistance of a second heater that has a power output three times as large at the same operating voltage? A. R 9 B. R 3 C. 3R D. 9R 5 9. 10. A magnetic force acts on an electric charge in a magnetic field when A. the charge is not moving. B. the charge moves in the direction of the magnetic field. C. the charge moves in the opposite direction to the magnetic field. D. the charge moves at right angles to the lines of the magnetic field. Three equal point charges X, Y and Z are fixed in the positions shown. Z q3 1 .0 m 90 X 1 .0 m q1 Y q2 The distance between q1 and q2 and the distance between q2 and q3 is 1.0 m. The electric force between the charges at X and Y is F. The electric force between the charges at X and Z is A. F . 2 F 2 B. C. F. D. 2F. . 6 11. Two charges of magnitude +2Q and −plainQ are situated as shown below. At which point is the electric field due to the two charges most likely to be zero? –Q +2Q A. 12. C. B. D. The diagram below shows two long parallel plates that are oppositely charged. A positive test charge +q is placed along the dotted line XY. +q X Y The charge +q is moved from X to Y. Which one of the following best shows the variation with distance d from X of the magnitude F of the force on +q? 7 A. F 0 B. F X Y C. F 0 13. 0 d X Y d X Y d D. F X Y 0 d The currents in two parallel wires are I and 3I in the directions shown in the diagram below. wire 1 wire 2 I 3I The magnetic force on wire 2 due to the current in wire 1 is F. The magnitude of the force on wire 1 due to the current in wire 2 is A. F . 3 B. F . 2 C. F. D. 3F. 8 14. In the circuit below the battery has emf 6.0 V and negligible internal resistance. The three resistors each have resistance 10 . A high resistance voltmeter is connected as shown. 6.0 V 10 10 10 V The reading of the voltmeter is 15. A. 2.0 V. B. 3.0 V. C. 4.0 V. D. 6.0 V. X and Y are two identical conducting spheres separated by a distance d. X has a charge +6 μC and Y has a charge –2 μC. The electric force between them is + F (ie attractive). The spheres are touched together and are then returned to their original separation d. The force between them now is A. +F. C. 16. 17. F . 3 B. –F. D. F . 3 A conductor of constant resistance dissipates 6.0 W of power when the potential difference across it is 12 V. The power that will be dissipated in this conductor when the potential difference across it is 24 V is A. 6.0 W. B. 12 W. C. 24 W. D. 48 W. OMIT 9 18. The graphs below are the current-voltage (I-V) characteristics of three electrical components P, Q and R. component P component Q I 0 component R I V 0 0 0 I 0 V V 0 Which component(s) has (have) constant resistance? A. P only B. R only C. P and Q only D. P and R only A resistor of resistance 1.0 is connected in series with a battery. The current in the circuit is 2.0 A. The resistor is now replaced by a resistor of resistance of 4.0 . The current in this circuit is 1.0 A. 19. A 2.0 A 1.0 4.0 The best estimate for the internal resistance of the battery is A. 1.0 . B. 2.0 . C. 4.0 . D. 5.0 . 10 20. A long, straight current-carrying wire is placed normal to the plane of the page. The current in the wire is into the plane of the page. Which of the following diagrams best represents the magnetic field around the wire? 21. A. B. C. D. The work done on a positive point charge of magnitude 3.0 nC as it is moved at constant speed from one point to another is 12 nJ. The potential difference between the two points is A. 0.0 V. B. 0.25 V. C. 4.0 V. D. 36 V. 11 22. The graph below shows the variation with current I of the potential difference V across a filament lamp. V / volts 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0.0 0.5 1.0 1.5 2.0 I / mA The resistance of the lamp when I = 1.5 mA is A. 950 . B. 400 . C. 0.95 . D. 0.40 . 23. In the circuit shown below, the cell has negligible internal resistance. Which of the following equations is correct? A. I1 = 2I2 B. I1 = 2I3 C. I2 = 2I3 D. I3 = 2I1 24. OMIT 25. OMIT 12 26. This question is about an electric circuit. A particular filament lamp is rated at 12 V, 6.0 mA. It just lights when the potential difference across the filament is 6.0 V. A student sets up an electric circuit to measure the I-V characteristic of the filament lamp. In the circuit, shown below, the student has connected the voltmeter and the ammeter into the circuit incorrectly. The battery has emf 12 V and negligible internal resistance. The ammeter has negligible resistance and the resistance of the voltmeter is 100 k. The maximum resistance of the variable resistor is 15. (a) Explain, without doing any calculations, whether there is a position of the slide S at which the lamp will be lit. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (b) Estimate the maximum reading of the ammeter. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (c) Complete the circuit diagram below showing the correct position of the voltmeter and of the ammeter in order to determine the I-V characteristic of the filament lamp. 13 27. This question is about electrical resistance. (a) Define electrical resistance. ................................................................................................................................... ................................................................................................................................... (b) (i) Three resistors, each of resistance 6.0 , are connected as shown below. 6.0 6.0 A 6.0 B Calculate the total resistance between point A and point B of this arrangement. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (ii) The arrangement in (b)(i) is now connected to two more resistors, as shown below. Each resistor is of resistance 6.0 . 6.0 6.0 6.0 A 6.0 B C 6.0 D Using your answer in (b)(i), deduce that the total resistance between point C and point D is 8.4 . 14 28. This question is about magnetic fields. (a) Using the diagram below, draw the magnetic field pattern of the Earth. North Earth (b) State what other object produces a magnetic field pattern similar to that of the Earth. ................................................................................................................................... (c) A long vertical wire passes through a sheet of cardboard that is held horizontal. A small compass is placed at the point P and the needle points in the direction shown. cardboard sheet direction of compass needle P A current is passed through the wire and the compass needle now points in a direction that makes an angle of 30 to its original direction as shown below. 15 direction of compass needle with current in wire cardboard sheet 30 P original direction of compass needle Draw an arrow on the wire to show the direction of current in the wire. Explain why it is in the direction that you have drawn. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... 16