Physics 3 20/21 make up examination paper 1

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Physics 3 20/21 make up examination paper 1. [1 mark] A cell is connected in series with a 2.0Ω resistor and a switch. The voltmeter is connected across the cell and reads 12V when the switch is open and 8.0V when the switch is closed. What is the internal resistance of the cell? A. 1.0 Ω B. 2.0 Ω C. 3.0 Ω D. 4.0 Ω 2. [1 mark] The diagram shows two long wires X and Y carrying identical currents in the same direction. The direction of the force experienced by Y is A. to the left. B. to the right. C. into the plane of the page. D. out of the plane of the page. 1 Physics 3 20/21 make up examination paper 3. [1 mark] Two resistors of resistance 10 Ω and 20 Ω are connected in parallel to a cell of negligible internal resistance. The energy dissipated in the 10 Ω resistor in one second is Q. What is the energy dissipated in one second in the 20 Ω resistor? ???? ???? A. 4 B. 2 C. 2Q D. 4Q 4. [1 mark] The graph shows the I–V characteristics of two resistors. When resistors X and Y are connected in series, the current in the resistors is 2.0 A. What is the resistance of the series combination of X and Y? A. 7.0 Ω B. 1.3 Ω C. 1.1 Ω D. 0.14 Ω 2 Physics 3 20/21 make up examination paper 5. [1 mark] Two isolated point charges, -7 μC and +2 μC, are at a fixed distance apart. At which point is it possible for the electric field strength to be zero? 6. [1 mark] A long straight wire carries an electric current perpendicularly out of the paper. Which of the following represents the magnetic field pattern due to the current? 7. [1 mark] The circuit shows a resistor R connected in series with a battery and a resistor of resistance 10 ????. The emf of the battery is 20 V and it has negligible internal resistance. The current in the circuit is 1.0 A. Which of the following is the resistance of R? A. 1.0 ???? B. 2.0 ???? C. 10 ???? D. 20 ???? 3 Physics 3 20/21 make up examination paper 8. [1 mark] Two 6 ???? resistors are connected in series with a 6 V cell. A student incorrectly connects an ammeter and a voltmeter as shown below. The readings on the ammeter and on the voltmeter are 9. [1 mark] An electron is travelling in a region of uniform magnetic field. At the instant shown, the electron is moving parallel to the field direction. The magnetic force on the electron is A. upwards. B. downwards. C. to the right. D. zero. 4 Physics 3 20/21 make up examination paper 10. [1 mark] A positively charged particle enters the space between two charged conducting plates, with a constant velocity directed parallel to the plates, as shown. The top plate is positively charged and the bottom plate is negatively charged. There is a magnetic field in the shaded region PQRS. The particle continues to move in a horizontal straight line between the plates. Which of the following correctly describes the magnetic field direction? A. Into plane of paper B. Out of plane of paper C. Up D. Down 11. [1 mark] A cylindrical resistor of volume V and length l has resistance R. The resistor has a uniform circular cross-section. What is the resistivity of the material from which the resistor is made? ???? A. ????????2 B. ????2???? ???? C. ???????? ????2 ????2 D. ???????? 12. [1 mark] Three fixed charges, +Q, –Q and –2Q, are at the vertices of an equilateral triangle. What is the resultant force on an electron at the centre of the triangle? 5 Physics 3 20/21 make up examination paper 13. [1 mark] The graph shows the variation of current I in a device with potential difference V across it. What is the resistance of the device at P? A. zero B. 0.1Ω C. 10Ω D. infinite 14. [1 mark] A circuit consists of a cell of electromotive force (emf) 6.0V and negligible internal resistance connected to two resistors of 4.0Ω. The resistance of the ammeter is 1.0 Ω. What is the reading of the ammeter? A. 2.0A B. 3.0A C. 4.5A D. 6.0A 6 Physics 3 20/21 make up examination paper 15. [1 mark] A circuit consists of a cell of electromotive force (emf) 6.0V and negligible internal resistance connected to two resistors of 4.0Ω. The ammeter has resistance equal to 1.0Ω and the voltmeter is ideal. What are the readings of the ammeter and the voltmeter? 16. [1 mark]A wire of uniform circular cross-section is replaced in an electrical circuit. The new wire has the same length and same resistance but half the diameter of the old wire. resistivity of the new wire What is the ratio resistivity of the old wire ? 1 A. 4 1 B. 2 2 C. 1 4 D. 1 7 Physics 3 20/21 make up examination paper 17. [1 mark] A circuit is formed by connecting a resistor between the terminals of a battery of electromotive force (emf) 6 V. The battery has internal resistance. Which statement is correct when 1 C of charge flows around the complete circuit? A. 6 V is the potential difference across the resistor. B. 6 J of thermal energy is dissipated in the battery. C. 6 J of chemical energy is transformed in the battery. D. 6 J of thermal energy is dissipated in the resistor. 18. [1 mark] Four resistors are connected as shown. What is the total resistance between X and Y? A. 3 Ω B. 4 Ω C. 6 Ω D. 24 Ω 19. [1 mark] What is the definition of electric current? A. The ratio of potential difference across a component to the resistance of the component B. The power delivered by a battery per unit potential difference C. The rate of flow of electric charge D. The energy per unit charge dissipated in a power supply 8 Physics 3 20/21 make up examination paper 20. [1 mark] A long, straight, current-carrying wire is placed between a pair of magnets as shown. What is the direction of the force on the wire? 21. [1 mark] An ion follows a circular path in a uniform magnetic field. Which single change decreases the radius of the path? A. Increasing the mass of the ion B. Increasing the charge of the ion C. Increasing the speed of the ion D. Decreasing the magnetic flux density of the field 22. [1 mark] The diagram shows an electric circuit containing a potentiometer of maximum resistance R. The potentiometer is connected in series with a resistor also of resistance R. The electromotive force (emf) of the battery is 6 V and its internal resistance is negligible 9 Physics 3 20/21 make up examination paper . The slider on the potentiometer is moved from P1 to P2. Which graph shows the variation of the voltmeter V reading with slider distance d? Answer sheet 1 2 3 4 5 6 7 8 9 14 15 16 17 18 19 20 21 22 10 10 11 12 13 Physics 3 20/21 make up examination paper 23a. [2 marks] Part 2 Electrical resistance A resistor of resistance 1.5Ω is made from copper wire of radius 0.18mm. The resistivity of copper is 1.7×10–8Ωm. Determine the length of copper wire used to make the resistor. 23b. [6 marks] The manufacturer of the resistor in (a) guarantees that the resistance is within 10% of 1.5Ω, provided that the power dissipation in the resistor does not exceed 1.0W. (i) Suggest why the resistance of the resistor might be greater than 1.65Ω if the power dissipation in the resistor is greater than 1.0W. (ii) Show that, for a power dissipation of 1.0W, the current in a resistor of resistance 1.5Ω is 0.82A. 11 Physics 3 20/21 make up examination paper (iii) The 1.5Ω resistor is connected in series with a variable resistor and battery of emf 6.0V and internal resistance 1.8Ω. Estimate the resistance R of the variable resistor that will limit the current to 0.82A. 24a. [2 marks] This question is in two parts. Part 1 is about energy resources. Part 2 is about electric fields. 12 Physics 3 20/21 make up examination paper Part 2 Electric fields An isolated metal sphere is placed in a vacuum. The sphere has a negative charge of magnitude 12 nC. Outside the sphere, the electric field strength is equivalent to that of a point negative charge of magnitude 12 nC placed at the centre of the sphere. The radius ???? of the sphere is 25 mm. Show that the magnitude of the electric field strength at the surface of the sphere is about 2 × 105 N C−1 . 24b. [2 marks] On the axes, draw a graph to show the variation of the electric field strength ???? with distance ???? from the centre of the sphere. 13 Physics 3 20/21 make up examination paper 24c. [2 marks] An electron is initially at rest on the surface of the sphere. Calculate the initial acceleration of the electron. 24d. [2 marks] Discuss the subsequent motion of the electron. 25a. [2 marks] This question is in two parts. Part 1 is about kinematics and Newton’s laws of motion. Part 2 Electrical circuits The circuit shown is used to investigate how the power developed by a cell varies when the load resistance ???? changes. 14 Physics 3 20/21 make up examination paper The variable resistor is adjusted and a series of current and voltage readings are taken. The graph shows the variation with ???? of the power dissipated in the cell and the power dissipated in the variable resistor. An ammeter and a voltmeter are used to investigate the characteristics of a variable resistor of resistance ????. State how the resistance of the ammeter and of the voltmeter compare to ???? so that the readings of the instruments are reliable. 15 Physics 3 20/21 make up examination paper 25b. [3 marks] Show that the current in the circuit is approximately 0.70 A when ???? = 0.80 ????. 25c. [2 marks] The cell has an internal resistance. Outline what is meant by the internal resistance of a cell. 25d. [3 marks] Determine the internal resistance of the cell. 16 Physics 3 20/21 make up examination paper 25e. [2 marks] Calculate the electromotive force (emf) of the cell. 17 25b. [3 marks) Show that the current in the circuit is approximately 0.70 A when R = 0.80 2. 1. [1 mark] A cell is connected in series with a 2.0N resistor and a switch. The voltmeter is connected across the cell and reads 12V when the switch is open and 8.0V when the switch is closed. V 2.022 What is the internal resistance of the cell? Α. 1.0 Ω Β. 2.0 Ω C. 3.0 Ω D. 4.0 Ω 2. [1 mark] The diagram shows two long wires X and Y carrying identical currents in the same direction. Font Paragraph Styles Editir 1. [1 mark] A cell is connected in series with a 2.00 resistor and a switch. The voltmeter is connected across the cell and reads 12V when the switch is open and 8.0V when the switch is closed. V 2.022 What is the internal resistance of the cell? Α. 1.0Ω Β. 2.0 Ω C. 3.0 ΩD. 4.0Ω 2. [1 mark] The diagram shows two long wires X and Y carrying identical currents in the same direction. Font Paragraph Styles Editing Voice (iii) The 1.512 resistor is connected in series with a variable resistor and battery of emf 6.0V and internal resistance 1.82. 6.0V 1.812 H R f 1.532 Estimate the resistance R of the variable resistor that will limit the current to 0.82A.