1 What is an example of a device that changes chemical energy into electrical energy? (A) battery (B) generator (C) light bulb (D) transformer

Transcription

1 Assignment 1 Electricity Name: 1 What is an example of a device that changes chemical energy into electrical energy? (A) battery (B) generator (C) light bulb (D) transformer 2 What is the definition for the number of electrons that pass a certain point in a conductor in a given amount of time? (A) charge (B) electric current (C) potential difference (D) resistance 3 Which diagram correctly shows a series circuit containing an electrical source, an ammeter, a light bulb and a voltmeter? 4 When the rate of electron flow through a resistor with constant resistance is doubled, what happens to the voltage drop across the resistor? (A) It is doubled. (B) It is halved. (C) It is not affected. (D) It is quadrupled. 5 What unit is used to measure the rate of flow of electric charge? (A) ampere (B) coulomb (C) kilowatt hour (D) volt

2 6 Which device converts chemical energy to electrical energy? (A) microphone (B) solar panel (C) thermocouple (D) voltaic cell 7 Which unit is equivalent to the ohm? (A) A/J (B) J/s (C) V/A (D) V/C 8 The circuit shown consists of a dry cell, a switch and a light bulb all connected with some copper wire. Which energy transformation is NOT taking place in the circuit shown? (A) chemical electric (in the dry cell) (B) electric heat (in the light bulb) (C) electric heat (in the wire) (D) electric mechanical (in the switch) 9 The picture shows three resistors, a dry cell battery and four open switches. Which statement about the circuit is correct? (A) (B) (C) (D) If S 1, S 2 and S 3 are closed then current will flow through all three resistors. If S 2, S 3 and S 4 are closed then current will flow through R 2 and R3 If S 1, S 3 and S 4 are closed then current will flow through R 1 and R 3. If S 2, S 3 and S 4 are closed then current will flow through R By what factor does the resistance of a wire change when the length is doubled and the radius is doubled? (A) four times the original (B) one half the original (C) one quarter the original (D) twice the original 11 A source of electrical energy generated from crystals is known as (A) light energy (B) thermocouple (C) piezoelectricity (D) secondary battery 12 The graph at the right shows values of current and corresponding voltages as measured through a resistor. For what range of values can the resistor be considered ohmic? (A) Between 0 A and 0.14 A. (B) Between 0 A and 0.08 A. (C) Greater than 0.08 A. (D) Greater than 0.14 A 13 For the previous graph, what is the resistance when the current is 0.06 A? (A) There is not enough information to determine it from the graph. (B) 0.72 (C) (D) 200

3 14 The graphs of potential difference vs. current for four different resistors A, B, C and D are shown below. Which of the four resistors has the highest resistance at 4 V? 15 For the given circuit, in order to determine the current through resistor R 3 and the voltage drop across R, where should a voltmeter and an ammeter be placed? 3

4 16 The diagram below shows a circuit in which a copper wire connects points A and B. The electrical resistance between points A and B can be decreased by: (A) replacing the wire with a thicker copper wire of the same length (B) replacing the wire with a longer copper wire of same thickness (C) increasing the temperature of the copper wire (D) increasing the potential difference supplied by the battery 17 Two wires, A and B, are made from the same material. Wire A is twice the cross-sectional area and four times as long as wire B. How does the resistances of wire A compare to that of wire B? (A) equal to (B) 2 times as great (C) 4 times as great (D) 16 times as great 18 By which process does a solar calculator get its energy? (A) photo electricity (B) piezo-electricity (C) thermoelectricity (D) voltaic cell 19-8 Given the resisitivity of copper is Ùm, what is the resistance of a 2.00 m long -3 copper extension cord that has a diameter of m? (A) Ù (B) Ù (C) Ù (D) Ù 20 Wire A has a resistance of 12 Ù. Wire B, of the same material, is twice as long and has half the cross-sectional radius of wire A. What is the resistance of wire B? (A) 1.5 Ù (B) 12 Ù (C) 48 Ù (D) 96 Ù 21 What is the potential difference in a circuit if 1000 J of work are done in supplying a current of 2.0 A for 100s? (A) 0.2 V (B) 2.0 V (C) 5.0 V (D) 500 V 22 In order to move a charge of 0.75 C from point A to point B in an electric field, 3.26 J of energy are required. What is the electric potential difference between the two points? (A) 0.23 V (B) 2.4 V (C) 2.5 V (D) 4.3 V 23 A 6.00 V battery delivers 2.00 A for 1.00 min. What is the energy delivered? (A) 3.00 J (B) 12.0 J (C) 180 J (D) 720 J

5 24 Twenty joules of work are done in carrying 2.0 C of charge from X to Y. What is the potential difference between X and Y? (A) 0.10 V (B) 2.0 V (C) 10 V (D) 20 V 25 What is the energy supplied to 15 C of charge by a 2.0 V electric cell? (A) 0.03 J (B) 7.5 J (C) 13 J (D) 30 J 26 How much current passes through an electric toaster if it takes 945 C of charge to toast two slices of bread in 2.0 minutes? (A) A (B) 7.9 A (C) 673 A (D) 1890 A 27 A 7.0 V battery produces a current of 14 A. What is the resistance in the circuit? (A) 0.50 Ù (B) 7.0 Ù (C) 21 Ù (D) 98 Ù 28 What is the total voltage available, when six 12 V cells are connected in parallel? (A) 1.5 V (B) 2.0 V (C) 12 V (D) 72 V What is the current flowing if 4.0 x 10 electrons pass a point in 0.50 s? (A) A (B) 0.31 A (C) 6.3 A (D) 78 A 30 How many electrons are transferred when a 5.0 ìc charged rod touches an electroscope? (A) (B) (C) (D) What is the energy output from a 6.00 V battery delivering a current of 1.50 A for a time of 2.00 minutes? (A) 4.50 J (B) 18.0 J (C) 240 J (D) 1080 J 32 An electric clothes dryer uses a current of 30.0 A for 12 minutes to dry a load of clothes. This process gives off 5184 kj of heat energy. What is the potential difference across the dryer? (A) 12 V (B) 120 (C) 220 V (D) 240 V

6 33 A 1.0 m length of wire with a diameter of 0.40 cm has a resistance of What will be the resistance of the same material with a length of 10 m and a diameter of 0.10 cm? (A) (B) (C) (D) The diagram shows an electrical junction and four resistors. The currents for three of the resistors are shown. What is the magnitude of the current I 4? (A) 1.0 A (B) 2.0 A (C) 3.0 A (D) 9.0 A 35 What is the value of I 3 in the junction of wires below? (A) 2.2 A (B) 4.3 A (C) 6.5 A (D) 10.8 A 36 In the diagram below, what is the least number of switches that must be closed for there to be a current through the radio? (A) 1 (B) 2 (C) 3 (D) 4 37 What is the resistance of a simple circuit given the plot of potential difference (volts) vs current flow (milliamps) for the circuit? (A) 10 Ù (B) 40 Ù (C) 160 Ù (D) Ù 38 When S1 and S2 are both closed, all three light bulbs light up. Under what conditions will both B and C fail to light? (A) Bulb A burns out. (B) Bulb B burns out. (C) S1 is opened but S2 remains closed. (D) S2 is opened but S1 remains closed. 39 In the diagram below, when switch S is opened as shown, which of the following is true? (A) lamp C only will stay lit (B) lamp B and C will stay lit (C) lamps A and C will stay lit (D) no lamps will stay lit

7 40 In the space below construct a parallel circuit containing the following circuit elements {4} 1-15 V power supply Ù bulb in parallel with 1-50 Ù bulb 1 switch that controls the entire circuit 1 switch that can shut down the 100 Ù bulb only 1 fuse that protects the circuit An ammeter that measures the current through the 50 Ù bulb A voltmeter that measures the voltage dropped on the 100 Ù bulb 41 A student measured the potential difference across, and the current through, two circuit elements, X and Y, and obtained the following data. (ii) Which element obeys Ohm s law? Explain. (iii) Calculate the resistance of the element in (ii).

8 42 A toaster designed to operate at 120 V draws a current of 8.3 A. It is mistakenly connected to a source of 240 V. A What current will it draw when connected to the 240 V source? {2} B What is the resistance of the toaster? {2} 43 A high voltage power line has a resistivity of Ù m, a diameter of 2.2 cm and carries a current of 50.0 A. If a bird lands on the power line, calculate the distance between the bird s feet if the potential difference across the bird s body is V. {4} 44 A piece of wire with diameter 0.20 mm and length 20.0 cm is found to have a resistance of 40.0 Find the resistance of each piece of wire that is made from the same material. a) diameter = 0.20 mm, length = 80.0 cm b) diameter = mm, length = 20.0 cm c) diameter = 0.60 mm, length = cm

9 45 a) A 350 ma current flows through a copper wire 5.6 m long and 1.4 mm in -8 diameter. Copper has a resistivity of 1.72 x 10 m. Find the potential difference of the circuit s source. b) A 1.0 m piece of wire with a cross-sectional radius of 3.0 mm has a resistance of x 10 Ù. If the wire is stretched until its cross-sectional radius is reduced to 1.0 mm, what would be the resistance of a 2.0 m long piece of the thinner wire? c) Suppose we have two pieces of copper wire of different lengths and cross-section areas, but both have the same resistance. Once piece is m long and the other is m long. The shorter wire has a cross-sectional radius of 1.80 mm. What is the cross-sectional radius of the longer wire?