ELEC166 Tutorial Questions Week 2 Q1. In the water flow model for electrical circuits, what quantity corresponds to the current flowing in a wire? Q2. In the water flow model for electrical circuits, what quantity corresponds to the voltage difference between two points in a circuit? Q3. In the water flow model for electrical circuits, what corresponds to a resistor, and how does the water model for a resistor (say, a wire) correspond to its electrical properties? Q4. Does the amount of current change when it flows through a resistor? How does this compare with the water flow model? Q5. A current (electron flow) carries energy. Where does the energy go when a current flows through a resistor? Q6. How many different ways can you connect together four 8Ω resistors, and what is the resistance value of each of these combinations? Q7. Three resistors are connected in series across a 6V battery. If the resistors have values 8Ω, 16Ω and 24Ω, what is the voltage across each resistor? Q8. If three 360Ω resistors are connected in parallel across a 6V battery, calculate the total current supplied by the battery. Q9. When a current of 5mA flows through a resistor of 5kΩ, what is the voltage across the resistor? What power will be dissipated by the resistor? Q10. Draw a circuit diagram for each of the following: a) Two resistors connected in parallel and then connected in series with a DC voltage source. b) Two resistors and a DC voltage source all joined in series. c) Two resistors connected in parallel and then connected in parallel with a series combination of three resistors. This arrangement is then connected in series with a DC voltage source and a diode. If the values of all the resistors are 1Ω and the voltage source is 5V, calculate the current supplied by the voltage source. Assume here that the diode behaves like a simple resistor of value 100Ω. Q11. Match the following symbols with their names. ELEC166 Tutorial Week 2 Page 1 resistor capacitor switch current source DC voltage source terminals inductor NO connection battery connection diode Q12. Calculate the output voltage across the lower 10Ω resistor in the following voltage divider circuit. 5Ω 15V 10Ω 10Ω Output Q13. Examine the following circuit diagram: R1 R3 R2 A R5 R6 R7 R8 R9 R10 R4 R13 R11 R12 (a) What would you do to measure the potential difference across R7? (b) Which resistors’ current in the circuit does the ammeter measure? (c) How would you modify the circuit so that you can measure the current flowing through R1? Which resistor will also have the same amount of current flowing through it? Why? ELEC166 Tutorial Week 2 Page 2 (d) In a series of circuit diagrams, successively replace parts of the circuit by their equivalent circuits, and reduce the whole circuit to a single voltage source and resistor. Assume that the value of each resistor is 1kΩ and the internal resistance of the ammeter is zero. Q14. Show that, when N resistors, each having resistance R, are connected in parallel, the total resistance is R/N. Q15. Here are three resistor networks: 1 A 1Ω C 2Ω 3Ω B 4Ω 2Ω 2 A 3Ω B 1Ω C 4Ω 5Ω A 3 1Ω C 2Ω 5Ω 3Ω B 4Ω 6Ω (a) For each of the three networks, calculate the resistance as seen between points A and B. (b) For each of the three networks, calculate the resistance as seen between points C and B. (c) If instead points A and B were connected together (i.e. by a short circuit), calculate the resistance as seen between points C and B for each of the three networks. ELEC166 Tutorial Week 2 Page 3