IB HYSICS Name: DEIL HYSICS eriod: Date: # Marks: BADDEST CLASS ON CAMUS TSOKOS LSN 5-1 TO 5-5 TEST REIEW 4. This question is about forces on charged particles. (a) (b) A charged particle is situated in a field of force. Deduce the nature of the force-field (magnetic, electric or gravitational) when the force on the particle (i) (ii) (iii) is along the direction of the field regardless of its charge and velocity; is independent of the velocity of the particle but depends on its charge; depends on the velocity of the particle and its charge. An electron is accelerated from rest in a vacuum through a potential difference of 2.1 k. Deduce that the final speed of the electron is 2.7 1 7 m s 1. The electron in (b) then enters a region of uniform electric field between two conducting horizontal metal plates as shown below. +95 (5) (3) ath of electron 2.7 1 7 m s 1 2.2 cm 12 cm The electric field outside the region of the plates may be assumed to be zero. The potential difference between the plates is 95 and their separation is 2.2 cm. As the electron enters the region of the electric field, it is travelling parallel to the plates. (c) (i) On the diagram above, draw an arrow at to show the direction of the force due to the electric 1
(d) (e) (ii) field acting on the electron. Calculate the force on the electron due to the electric field. The plates in the diagram above are of length 12 cm. Determine (i) (ii) the time of flight between the plates. the vertical distance moved by the electron during its passage between the plates. Suggest why gravitational effects were not considered when calculating the deflection of the electron. 6. 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. 8. 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. 9. The diagram below shows two lines of equipotential in a region of a uniform electric field. Line X has a potential of +5 and line Y has a potential of +1. The distance between X and Y is 2. cm. (3) (3) 2
X Y +5 +1 Which one of the following correctly gives the direction of the electric field and its strength? Direction Strength / cm 1 A. X Y 25 B. X Y 1 C. Y X 25 D. Y X 1 12. This question is about the electric potential due to a charged sphere. (a) 2. cm Define electric potential at a point in an electric field. The diagram below shows an isolated, metal sphere in a vacuum that carries a negative electric charge of 9. nc. (3) (b) (c) (d) On the diagram above draw (i) (ii) arrows to represent the electric field pattern in the region outside the charged sphere. lines to represent three equipotential surfaces in the region outside the sphere. The potential differences between the lines are to be equal in value. Explain how the lines representing the equipotential surfaces that you have sketched indicate that the strength of the electric field is decreasing with distance from the centre of the sphere. The electric field strength at all points inside the conductor is zero. On the axes below, draw a graph to show the variation with distance r from the centre of the sphere of the potential. The dotted line is drawn at r = a where a is the radius of the sphere. (Note: this is a sketch graph; you do not need to 3 (3)
add values to the axes.) a r (e) The electric field strength at the surface of the sphere and at points outside the sphere may be determined by assuming that the sphere acts as though a point charge of magnitude 9. nc is situated at its centre. The radius of the sphere is 4.5 1 2 m. Deduce that the potential at the surface of the sphere is 18. An electron is initially at rest at the surface of the sphere. (f) (i) Describe the path followed by the electron as it leaves the surface of the sphere. (ii) Determine the speed of the electron when it reaches a point a distance.3 m from the centre of the sphere. 13. Two isolated spheres X and Y of unknown materials are touching one another as shown below. sphere X, earthed sphere Y, negatively charged (4) (Total 18 marks) 4
Sphere Y is negatively charged and sphere X is earthed. The earth connection is removed from sphere X and then the spheres are separated as shown below. sphere X, positively charged sphere Y, negatively charged Sphere X is found to be positively charged and sphere Y remains negatively charged. Which of the following describes the nature of the materials from which the spheres are made? Sphere X Sphere Y A. Insulator Insulator B. Insulator Conductor C. Conductor Insulator D. Conductor Conductor 15. This question is about electric charge at rest. (a) Define electric field strength at a point in an electric field. Four point charges of equal magnitude, are held at the corners of a square as shown below. +Q 2a +Q 2a The length of each side of the square is 2a and the sign of the charges is as shown. The point is at the centre of the square. (b) (i) Deduce that the magnitude of the electric field strength at point due to one of the point kq charges is equal to. 2 2a (ii) Q On the diagram above, draw an arrow to represent the direction of the resultant electric field at point. (iii) Determine, in terms of Q, a and k, the magnitude of the electric field strength at point. Q 5
16. The diagram below shows electric field lines in a region of space. (3) (Total 8 marks) X Y Which of the following diagrams best shows the variation with distance d of the potential along the line XY? A. B. X Y d X Y d C. D. X Y d X Y d 18. An isolated conducting sphere of radius r is positively charged. 6
Which one of the following graphs best shows the variation with distance x from the centre of the sphere of the electric potential? A. B. r x r x C. D. r x r 22. The diagram below shows some equipotential lines in an electric field. +3 +29 +28 +27 +26 +25 x X Y The magnitude of the electric field strength at X is E X and at Y is E Y. Which one of the following correctly compares E X and E Y and gives the correct direction of the electric field? Magnitude of field strengths Direction of field A. E X E Y X Y B. E X E Y Y X C. E X E Y X Y D. E X E Y Y X 23. The diagram below shows a charged rod R suspended by insulating strings. When a stationary rod S is placed nearby, rod R is attracted towards it. 7
rod R rod S insulated stand Consider the following statements regarding the possible nature of the rod S. I. Rod S is charged II. Rod S is an uncharged insulator. III. Rod S is an uncharged conductor. Which statement(s) can explain the attraction of rod R to rod S? A. I only B. II only C. III only D. I and III only 26. A positively charged rod is brought close to an earthed sphere S, as shown below. S The earth connection to the sphere is removed and then the charged rod is removed. The sphere S is found to be negatively charged. Which one of the following describes the material of S and the movement of charge between S and earth? Material of S Movement of charge A. conductor negative charge moves from earth to S B. insulator negative charge moves from earth to S C. conductor positive charge moves from S to earth D. insulator positive charge moves from S to earth 27. Two charges of magnitude +2Q and Q are situated as shown below. At which point is the electric field due to the two charges most likely to be zero? +2Q Q A. B. C. D. 8
29. The graphs below are the current-voltage (I-) characteristics of three electrical components, Q and R. component component Q component R I I I Which component(s) has (have) constant resistance? A. only B. R only C. and Q only D. and R only 33. Two charged plastic balls are separated by a distance d in a vertical insulating tube, as shown. tube balls d The charge on each ball is doubled. Coulomb s law applies to the force between the balls and friction with the walls of the tube is negligible. What is now the separation of the balls? A. B. d 2 d C. 2d D. 4d 37. The variation with potential difference of the current I in an electric lamp is shown below. I I p p At point, the current is I p, the potential difference is p and the gradient of the tangent to the curve is G. What is the resistance of the lamp at point? 9
A. 1 G B. G C. I p D. I p p p 39. Which one of the following shows a correct circuit, using ideal voltmeters and ammeters, for measuring the I- characteristic of a filament lamp? A. A B. A C. D. A A 4. This question is about electrical energy and associated phenomena. Current electricity A cell of electromotive force (emf) E and internal resistance r is connected in series with a resistor R, as shown below. E r R The cell supplies 8.1 1 3 J of energy when 5.8 1 3 C of charge moves completely round the circuit. The current in the circuit is constant. 1
(i) (ii) Calculate the emf E of the cell. The resistor R has resistance 6. Ω. The potential difference between its terminals is 1.2. Determine the internal resistance r of the cell. (iii) Calculate the total energy transfer in the resistor R. (iv) Describe, in terms of a simple model of electrical conduction, the mechanism by which the energy transfer in the resistor R takes place. 42. In the circuit below, which meter is not correctly connected? (3) (5) (Total 12 marks) A 1 3 A 2 4 A. 1 B. 2 11
C. 3 D. 4 44. In the circuit below, n charge carriers pass the point in a time t. Each charge carrier has charge q. The current in the circuit is given by the expression A. q. t B. nq. t C. qt. n D. nqt. 49. The diagrams below show combinations X, Y and Z of three resistors, each resistor having the same resistance. Which one of the following shows the resistances of the combinations in increasing order of magnitude? lowest combination X highest A. Y X Z B. Z X Y C. X Y Z D. Z Y X combination Y combination Z 52. A heater has a resistance R when the potential difference across it is 12. In the circuit below, it is connected in series with a 36 supply and a resistor S. 12
36 S To ensure that the potential difference across the heater is 12, the resistance of the resistor S should be A. R. 2 B. 2R. 3 C. 3R. 2 D. 2R. 54. The drift velocity of the electrons in a copper wire in which there is an electric current is A. equal to the speed of light. B. close to that of the speed of light. C. of the order of a few kilometres per second. D. of the order of a few millimetres per second. 61. Which of the following is a correct statement of Ohm s law? A. The resistance of a conductor is always constant. B. The current in a conductor is always proportional to the potential difference across the conductor. C. The resistance of a conductor increases with increasing temperature. D. The resistance of a conductor is constant only if the temperature of the conductor is constant. 62. A resistor of resistance 1. is connected in series with a battery. The current in the circuit is 2. A. The resistor is now replaced by a resistor of resistance of 4.. The current in this circuit is 1. A. 2. A A 1. The best estimate for the internal resistance of the battery is A. 1.. B. 2.. C. 4.. D. 5.. 63. Define emf and state Ohm s law. 4. 13
emf:...... Ohm s law:...... 67. A metal conductor is negatively charged. It is connected to earth using a metal wire, as illustrated below. negatively-charged conductor wire earth What is the movement of charge as the conductor is earthed? A. ositive charge moves from earth to the conductor. B. Negative charge moves to earth from the conductor. C. Negative charge moves from the conductor and positive charge moves from earth. D. ositive charge from the wire moves to the conductor and negative charge moves to earth. 14