Name: Period: Date: IB-1 Practice Electrical Currents, Resistance, and Circuits Multiple Choice Questions 1. In the circuit below, which meter is not correctly connected? A 1 3 A 2 4 A. 1 B. 2 C. 3 D. 4 2. 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 A. q nq qt. B.. C.. D. nqt. t t n 3. The diagrams below show combinations X, Y and Z of three resistors, each resistor having the same resistance. combination X combination Y combination Z Which one of the following shows the resistances of the combinations in increasing order of magnitude? (see next page)
lowest highest A. Y X Z B. Z X Y C. X Y Z D. Z Y X 4. 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. A battery is connected to a resistor as shown below. energy transferred E B energy transferred E R The battery transfers energy E B when charge Q passes completely around the circuit and the resistor transfers energy E R. The emf of the battery is equal to E A. R. Q E B. B. Q E B + E C. R. Q EB E D. R. Q 6. The resistors in each of the circuits shown below each have the same resistance. circuit P circuit Q circuit S Which of the following gives the circuits in order of increasing total resistance? A. P Q S B. Q P S C. S Q P D. P S Q 2
7. In the circuit below, the battery has negligible internal resistance. Lamps L, M and N which have different resistance are connected as shown. L M N Which one of the following is always true? A. Lamps L and N have the same current through them. B. Lamps L and M have the same current through them. C. Lamps L and N have the same potential difference across them. D. Lamps L and M have the same potential difference across them. 8. In the circuit below the battery has emf 6.0 and negligible internal resistance. The three resistors each have resistance 10 Ω. A high resistance voltmeter is connected as shown. 6.0 10Ω 10Ω 10Ω The reading of the voltmeter is A. 2.0. B. 3.0. C. 4.0. D. 6.0. 3
9. The graphs below are the current-voltage (I-) characteristics of three electrical components P, Q and R. component P component Q component R I I I 0 0 0 0 0 0 Which component(s) has (have) constant resistance? A. P only B. R only C. P and Q only D. P and R only (1) 10. The graph below shows the variation with current I of the potential difference across a filament lamp. / 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 Ω. B. 400 Ω. C. 0.95 Ω. D. 0.40 Ω. (1) 4
Free Response Question 1. This question is about electrical resistance. (a) Define electrical resistance. (b) (i) Three resistors, each of resistance 6.0 Ω, are connected as shown below. 6.0W A 6.0W 6.0W Calculate the total resistance between point A and point B of this arrangement. B The arrangement in (b)(i) is now connected to two more resistors, as shown below. Each resistor is of resistance 6.0 Ω. 6.0W A 6.0W C 6.0W 6.0W 6.0W B D Using your answer in (b)(i), deduce that the total resistance between point C and point D is 8.4 Ω. (iii) One of the resistors in the arrangement shown in (b) becomes faulty. The resistance between point C and point D is found to be 6.0 Ω. On the diagram in (b) above, identify the faulty resistor by drawing a circle around it. Deduce the nature of the fault (i.e. open circuit or short circuit). 5
2. This question compares the electrical properties of two 12 filament lamps. A lamp is designed to operate at normal brightness with a potential difference of 12 across its filament. The current in the filament is 0.50 A. (a) For the lamp at normal brightness, calculate (i) the power dissipated in the filament. the resistance of the filament. In order to measure the voltage-current (-I) characteristics of a lamp, a student sets up the following electrical circuit. 12 battery (b) On the circuit above, add circuit symbols showing the correct positions of an ideal ammeter and an ideal voltmeter that would allow the -I characteristics of this lamp to be measured. 6
2. (continued) The voltmeter and the ammeter are connected correctly in the previous circuit. (c) Explain why the potential difference across the lamp (i) cannot be increased to 12. cannot be reduced to zero. An alternative circuit for measuring the -I characteristic uses a potential divider. (d) (i) Draw a circuit that uses a potential divider to enable the -I characteristics of the filament to be found. Explain why this circuit enables the potential difference across the lamp to be reduced to zero volts. 7
2. (continued) The graph below shows the -I characteristic for two 12 filament lamps A and B. Potential difference / 12 lamp A lamp B 0 0 0.5 1.0 current / A (e) (i) Explain why these lamps do not obey Ohm s law. State and explain which lamp has the greater power dissipation for a potential difference of 12. The two lamps are now connected in series with a 12 battery as shown below. 12 battery lamp A lamp B 8
2. (continued) (f) (i) State how the current in lamp A compares with that in lamp B. Use the -I characteristics of the lamps to deduce the total current from the battery. (iii) Compare the power dissipated by the two lamps. 9