D W. (Total 1 mark)

Transcription

1 1. One electronvolt is equal to A C. B J. C V. D W. 2. A battery of internal resistance 2 Ω is connected to an external resistance of 10 Ω. The current is 0.5 A. What is the emf of the battery? A. 1.0 V B. 5.0 V C. 6.0 V D V 3. This question is about electric circuits. (a) Define (i) electromotive force (emf ) of a battery. (1) IB Questionbank Physics 1

2 (ii) electrical resistance of a conductor. (1) (b) A battery of emf ε and negligible internal resistance is connected in series to two resistors. The current in the circuit is I. (i) State an equation giving the total power delivered by the battery. (1) (ii) The potential difference across resistor R 1 is V 1 and that across resistor R 2 is V 2. Using the law of the conservation of energy, deduce the equation below. ε = V 1 + V 2 IB Questionbank Physics 2

3 (c) The graph shows the I-V characteristics of two conductors, X and Y. On the axes below, sketch graphs to show the variation with potential difference V of the resistance of conductor X (label this graph X) and conductor Y (label this graph Y). You do not need to put any numbers on the vertical axis. (3) IB Questionbank Physics 3

4 (d) The conductors in (c) are connected in series to a battery of emf ε and negligible internal resistance. The power dissipated in each of the two resistors is the same. Using the graph given in (c), (i) determine the emf of the battery. (ii) calculate the total power dissipated in the circuit. (Total 12 marks) IB Questionbank Physics 4

5 4. A light-dependent resistor (LDR) and a fixed resistor are connected in the potential divider circuit shown below. The voltmeter reads 3.0 V. Which of the following changes would cause the reading on the voltmeter to increase? A. Swapping the positions of the LDR and the fixed resistor B. Increasing the resistance of the fixed resistor C. Increasing the amount of light shining on the LDR D. Decreasing the amount of light shining on the LDR IB Questionbank Physics 5

6 5. 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 Ω 6. This question is about electrical resistance. (a) A resistor of resistance 1.5 Ω is made from copper wire of radius 0.18 mm. The resistivity of copper is Ω m. Determine the length of copper wire used to make the resistor IB Questionbank Physics 6

7 (b) The manufacturer of the resistor in (a) guarantees that the resistance is within 10 % of 1.5 Ω, provided that the power dissipation in the resistor does not exceed 1.0 W. (i) Suggest why the resistance of the resistor might be greater than 1.65 Ω if the power dissipation in the resistor is greater than 1.0 W. (ii) Show that, for a power dissipation of 1.0 W, the current in a resistor of resistance 1.5 Ω is 0.82 A. (1) IB Questionbank Physics 7

8 (iii) The 1.5 Ω resistor is connected in series with a variable resistor and battery of emf 6.0 V and internal resistance 1.8 Ω. Estimate the resistance R of the variable resistor that will limit the current to 0.82 A. (3) (Total 8 marks) 7. The electromotive force (emf) of a cell is defined as A. the power supplied by the cell per unit current from the cell. B. the force that the cell provides to drive electrons round a circuit. C. the energy supplied by the cell per unit current from the cell. D. the potential difference across the terminals of the cell. IB Questionbank Physics 8

9 8. This question is about an electrical heater. An electrical heater consists of two heating elements E 1 and E 2. The elements are connected in parallel. Each element has a switch and is connected to a supply of emf 240 V. The supply has negligible internal resistance. Element E 1 is made from wire that has a cross-sectional area of m 2. The resistivity of the wire at the operating temperature of the element is Ωm. (a) (i) The total length of wire is 4.5 m. Show that the resistance of E 1 is 73 Ω. (1) (ii) Calculate the power output of E 1 with only this element connected to the supply. IB Questionbank Physics 9

10 (iii) Element E 2 is made of wire of the same cross-section and material as E 1. The length of wire used to make E 2 is 1.5 m. Determine the total power output when both E 1 and E 2 are connected to the supply. (3) (iv) With reference to the power output, explain why it would be inappropriate to connect the heating elements in series. (3) (b) Each element in the electrical heater is wound as a coil as shown. Each turn of the coil may be considered to act as a current-carrying long straight wire. IB Questionbank Physics 10

11 (i) On the diagram, draw the magnetic field around a current-carrying long straight wire. The arrow shows the direction of the current. (3) (ii) State and explain whether the turns of wire will attract or repel one another. (3) (Total 15 marks) 9. An alpha particle is accelerated through a potential difference of 10 kv. Its gain in kinetic energy is A. 10 ev. B. 20 ev. C. 10 kev. D. 20 kev. IB Questionbank Physics 11

12 10. A copper wire, of electric resistance R, has a length L and a cross-section area S. Another S copper wire has a length 2L and a cross-section area of. Which of the following is the 2 resistance of this wire? A. B. R 4 R 2 C. 2R D. 4R 11. This question is about electrical resistance and electric circuits. (a) Define resistance and state Ohm s law. Resistance: Ohm s law: (b) A resistor made from a metal oxide has a resistance of 1.5 Ω. The resistor is in the form of a cylinder of length m and radius m. Calculate the resistivity of the metal oxide IB Questionbank Physics 12

13 (c) The manufacturer of the resistor in (b) guarantees its resistance to be within ±10 % of 1.5 Ω provided the power dissipation in the resistor does not exceed 1.0 W. Calculate the maximum current in the resistor for the power dissipation to be equal to 1.0 W (d) The resistance of each of the resistors in the circuit below is measured to be 1.5 Ω with an accuracy of ±10 %. The cell has an emf of 2.0 V and negligible internal resistance. (i) Define emf. (1) IB Questionbank Physics 13

14 (ii) Determine the minimum and the maximum power that could be dissipated in this circuit. (3) (Total 10 marks) 12. The graph shows how the current I in a resistor varies with the voltage V applied across it. Which of the following gives the resistance of the resistor, when I = I 1? A. V I 1 1 B. The slope of the curve at the point (V 1, I 1 ) C. I V 1 1 D. The inverse of the slope of the curve at the point (V 1, I 1 ) IB Questionbank Physics 14

15 13. Two 10 Ω resistors are connected as shown. What is the resistance across PQ? A. 0 Ω B. 5 Ω C. 10 Ω D. 20 Ω 14. The circuit shows a resistor R connected in series with a battery and a resistor of resistance 10 Ω. 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 Ω B. 2.0 Ω C. 10 Ω D. 20 Ω IB Questionbank Physics 15

16 15. Two rectangular blocks, X and Y, of the same material have different dimensions but the same overall resistance. Which of the following equations is correct? A. resistivity of X length of X = resistivity of Y length of Y B. length of X cross sectional area of X length of Y = cross sectional area of Y C. resistivity of X cross sectional area of X = resistivity of Y cross sectional area of Y D. length of X cross sectional area of Y = cross length of Y sectional area of X 16. The tungsten filament of a lamp has a cross-sectional area A and length L. For a potential difference V across the filament, the current in the filament is I. The resistivity of the tungsten equals V A A.. I L I L B.. V A V L C.. I A D. I A V L IB Questionbank Physics 16

17 17. Which of the following is a correct unit of electromotive force (emf)? A. A Ω 1 B. Ω A 1 C. C J 1 D. J C This question is about electrical resistance. (a) A heating coil is to be made of wire of diameter m. The heater is to dissipate 980 W when connected to a 230 V d.c. supply. The material of the wire has resistivity Ω m at the working temperature of the heater. (i) Define electrical resistance. (1) (ii) Calculate the resistance of the heating coil at its normal working temperature. (iii) Show that the length of wire needed to make the heating coil is approximately 4 m. IB Questionbank Physics 17

18 (b) Three identical electrical heaters each provide power P when connected separately to a supply S which has zero internal resistance. On the diagram below, complete the circuit by drawing two switches so that the power provided by the heaters may be either P or 2P or 3P. (Total 7 marks) 19. The electronvolt is a unit of A. force. B. potential difference. C. energy. D. electric field strength. IB Questionbank Physics 18

19 20. A cell of emf ε and internal resistance r delivers current to a small electric motor. 450 C of charge flows through the motor and 9000 J of energy are converted in the motor J are dissipated in the cell. The emf of the cell is A. 4.0 V. B. 16 V. C. 20 V. D. 24 V. 21. A cylindrical conductor of length l, diameter D and resistivity ρ has resistance R. A different cylindrical conductor of resistivity 2 ρ, length 2l and diameter 2D has a resistance A. 2R. B. R. R C.. 2 R D.. 4 IB Questionbank Physics 19