Electric Currents B 4 & DC Circuits C 1/2 D 1/4 E 1 - PDF document

Slide 1 / 70 Slide 2 / 70 1 The length of an aluminum wire is quadrupled and the radius is doubled. By which factor does the resistance change? A 2 Electric Currents B 4 & DC Circuits C 1/2 D 1/4 E 1 Slide 3 / 70 Slide 4 / 70 2 A copper wire has a length L and cross-sectional 3 Which circuit has greater resistance between the area A. What happens to the resistivity of the wire terminals? if the length is doubled and cross-sectional area halved? A Four times as large A A B Two times as large B B C Stays the same C C D Half as large D D E Quarter as large E C and D Slide 5 / 70 Slide 6 / 70 4 Which circuits have the same resistance between 5 In the circuit shown above, what is the value of the the terminals? net resistance? A 1 Ω B 2 Ω A A and B C 3 Ω B B and C D 4 Ω C C and D E 6 Ω D D and A E C and A

Slide 7 / 70 Slide 8 / 70 6 What is the current in 4 - Ω resistor? 7 What is the voltage between points L and M? A 1A A 2 V B 2A B 3 V C 3A C 4 V D 4A D 3 V E 5A E 5 V Slide 9 / 70 Slide 10 / 70 8 A lamp L1, a voltmeter V, an ammeter A, and a battery with zero internal 9 Into which circuit should the battery be connected resistance are connected as shown above. Connecting another lamp L2 to obtain the greatest steady power dissipation? in series with the first lamp as shown by the dashed lines would A Increase the ammeter reading A B Decrease the ammeter reading B C Increase the voltmeter reading C D Decrease the voltmeter reading D E Produce no change in either meter reading E Slide 11 / 70 Slide 12 / 70 A A 10 Which circuit will retain stored energy if the 11 The five resistors shown below have the lengths B B battery is connected to it and then disconnected? and cross sectional areas indicated and are made of material with the same resistivity. Which has C C the smallest resistance? D D A A E E B B C C D D E E

Slide 13 / 70 Slide 14 / 70 12 Two capacitors are connected in parallel as shown 13 The circuit shown above left is made up of a above. A voltage V is applied to the pair. What is variable resistor and a battery with negligible internal resistance. A graph of the power P the ratio of charge stored on C 1 to the charge stored on C 2 , when C 1 = 3C 2 ? dissipated in the resistor as a function of the current I supplied by the battery is given above right. What is the emf of the battery? A 4/9 B 2/3 C 3/1 A 5 V D 3/2 B 8 V E 9/4 C 10 V D 20 V E 40 V Slide 15 / 70 Slide 16 / 70 14 The total equivalent resistance of the circuit 15 A heating spiral of resistance R converts shown on the diagram is: elec trical energy into thermal energy that is transferred to the liquid in which the spiral is immersed. If the voltage across the spiral is V, the thermal energy trans ferred to the liquid in time t A 3 Ω is: B 4 Ω C 5 Ω A Vrt D 6 Ω V 2 Rt B E 9 Ω VR 2 t C VRt 2 D V 2 t/R E Slide 17 / 70 Slide 18 / 70 16 In the circuit two identical resistors R are 17 The equivalent capacitance for this network is: connected in series with 8-Ω resistor and 12-V battery. What is the value of R if the current in the circuit I = 1 A? A 1 μF B 2 μF C 3 μF A 1 Ω D 4 μF B 2 Ω E 5 μF C 4 Ω D 12 Ω E 18 Ω

Slide 19 / 70 Slide 20 / 70 18 The charge stored in the circuit is: 19 What is the emf of the battery? A 6 μC A 2 V B 12 μC B 4 V C 48 μC C 3.6 V D 24 μC D 12 V E 36 μC E 18 V Slide 21 / 70 Slide 22 / 70 20 What is the potential difference across the 21 What power is dissipated by the 2-ohm internal terminals A and B of the battery? resistance of the battery? A 1.2 V A 0.06 W B 2.4 V B 1.2 W C 3.6 V C 3.2 W D 12.2 V D 0.08 W E 18.4 V E 4.8 W Slide 23 / 70 Slide 24 / 70 22 In the diagrams, resistors R 1 and R 2 are shown in two different 23 The product 3 amperes x3 volts x 3 seconds is connections to the same source of emf ε that has no internal resistance. equal to How does the power dissipated by the resistors in these two cases compare? A It is greater for the series connection. A 27 C B It is greater for the parallel connection. B 27 N C It is the same for both connections. C 27 J It is different for each connection, but D D 27 W one must know the values of R 1 and R 2 to know which is greater. E 27 N·A It is different for each connection, but one E must know the value of ε to know which is greater.

Slide 25 / 70 Slide 26 / 70 24 The electrical resistance of the part of the circuit 25 When there is a steady current in the circuit, the amount of charge passing a point per unit of time is: shown between point X and point Y is A the same everywhere in the circuit B greater at point X than at point Y A 4/3 Ω greater in the 2 Ω resistor than in the C B 2.5 Ω 5 Ω resistor the same in the 2 Ω resistor and in C 2.75 Ω D the 5 Ω resistor D 4.5 Ω greater in the 3 Ω resistor than in the E 5 Ω resistor E 6/5 Ω Slide 27 / 70 Slide 28 / 70 26 A certain coffeepot draws 2.0 A of current when it 27 What is the net capacitance of the circuit? is operated on 110 V household lines. If electrical energy costs 10 cents per kilowatt-hour, how much does it cost to operate the coffeepot for 5 A 3C hours? B 2C C 3/2 C A 2.4 cents D 2/3 C B 4.8 cents E C C 8.0 cents D 9.6 cents E 11 cents Slide 29 / 70 Slide 30 / 70 28 What is the net charge stored in the circuit? 29 What is the potential difference between the points X and Y? A CV A V B 3CV/2 B 1/3 V C 2CV/3 C 1/2 V D CV/2 D 2/3 V E CV/3 E 3/2 V

Slide 31 / 70 Slide 32 / 70 30 What is the net resistance of the circuit? 31 What is the current in the light bulb L 1 ? A 30 Ω A 1 A B 40 Ω B 2 A C 50 Ω C 3 A D 60Ω D 4 A E 80 Ω E 5 A Slide 33 / 70 Slide 34 / 70 32 Which light bulb or bulbs could burn out without 33 Four resistors and a capacitor are connected to an causing others to go out? 18 V battery with negligible internal resistance, as shown on the diagram. Initially the capacitor is disconnected from the battery – switch is open A Only L 1 B Only L 2 A Calculate the net resistance of the circuit. C Only L 3 and L 4 B Calculate the current in the 2-Ω resistor. D Only L 4 E Only L 5 C Calculate the current in the 3-Ω resistor. D Calculate the charge on the capacitor. E Calculate the energy stored in the capacitor. Slide 35 / 70 Slide 36 / 70 1. A physics student has an assignment to make an electrical heating system with the set of materials listed below: Free Response a. In a space above draw a diagram showing all the elements connected in one electrical circuit that can provide the maximum rate of heat produced. Use two meters in your circuit, they will help to measure the heat rate. The battery has an emf of 12 V and an internal resistance of 0.5 Ω and each heating coil has a resistance of 17.3 Ω. b. When the switch is closed, what is the current running through the battery? c. What is the terminal voltage on the battery? d. What is the rate of energy delivered by the heating system? e. If the switch is closed for 5 min, what is the total energy dissipated in the coils?