Chapter 9 Review
18. What is the current through a 1200 W hair dryer if it is connected to 120 V?
10A
17. A light bulb is connected to 120 V and uses 1.2 A. What is the power rating of this bulb?
144W
19. A 0.20 A current passes through a 450 resistor. Calculate the electric power "lost" in this resistor. (Hint: Use Ohm's law to find the voltage.)
18W
1. In terms of the number of pathways, what is the difference between a series circuit and a parallel circuit?
A series circuit contains only one pathway, whereas a parallel circuit contains more than one pathway.
10. What is the definition of power in terms of energy and time?
Energy is the product if power and time. E=Pt
20. Find the power rating of each lamp in the circuit below. (on paper)
Lamp 1 = 27 W, Lamp 2 = 18 W
21. List the following device usages in order of highest consumption of energy to lowest consumption of energy. (chart on paper)
Light bulb, hair dryer, microwave oven
8. State the relationship of power (P), voltage (V), and current (I).
Power is the product of voltage and current: P=VI.
2. Two resistors are connected in series. How does the current through the second resistor compare to the current through the first resistor?
The current through the seconds resistor is the same as the current through the first resistor.
3. A 6.0 V battery is connected to three resistors connected in series. What is the total voltage lost on the three resistors?
The total voltage lost on the three resistors: 6.0V
5. Two resistors are connected in parallel. How does the voltage on one resistor compare to the voltage on the second resistor?
The voltage is the same on both of the resistors.
16. In the circuit shown below, what would be the reading on the voltmeter V1 and the ammeter A1? (on paper)
V1 - 6.0 V, A1 = 2.0 A
14. In the circuit shown below, what would be the readings on the voltmeter V1, and the ammeter A1? (on paper)
V1= 5.0 V, A1 = 2.0 A
22. If the electric company charges 7 cents for every kWh of energy, calculate how much it costs for each of the following: (a) 5.0 kW stove used for 2.0 h (b) 200 W water heater used for 8.0 h
a) 70 cents b) 11 cents
9. (a) What two units are used for measuring electrical energy? (b) Which unit is larger?
a) Electrical energy is measured in joules (J) and kilowatt-hours (kWh) b) The kilowatt hours is the larger unit
7. (a) State the definition of power. (b) What unit is used to measure power?
a) Power is the rate at which energy is transformed. b) Power measures in Watts (W)
12. Give a non-electric example of a real life situation that represents: (a) a series circuit (b) a parallel circuit
a) Single lane bridge b) Entering a bus by two different doors
11. A battery and two light bulbs are all connected in series. (a) What happens to the second light bulb if the first one "burns out"? (b) Would the result be the same if the bulbs were connected in parallel? Explain.
a) The 2nd bulb goes out b) It would be different if the bulbs were connected in parallel. Even if one bulb burns out there is still a pathway for current through the second bulb and therefore it would stay lit.
15. A battery is connected to a resistor and the current leaving the battery is measured. What would happen to the current leaving the same battery if another resistor is: (a) connected in series with the original resistor? Explain your answer. (b) connected in parallel with the original resistor? Explain your answer.
a) The current would decrease because adding another resistor in series increases the total resistance of the circuit. b) The current would increase because adding another resistor in parallel decreases the total resistance of the circuit.
13. For each circuit below, state if the resistors are connected in series or parallel. Give a reason for your answer. (on paper)
a) The resistors are connected in parallel. Electronics leaving the battery have two pathways to return to the battery. b) The resistors are connected in series. Electrons leaving through both resistors in order to return to the battery.
6. (a) A current entering a junction point branches into two pathways. Describe the relationship between the current entering the junction point and the total current in the two pathways that leave the junction point. (b) If the two pathways have different resistances, will the current in each pathway be the same?
a) The total current leaving the junction point must be = the current entering the junction point. b) The current in the 2 pathways is different.
4. Complete each of the following sentences in your notebook, using "increases," "does not change," or "decreases." (a) Adding a resistor in series ___________ the total resistance of the circuit. (b) Adding a resistor in parallel __________ the total resistance of the circuit.
a) increases b) decreases
