A German physicist, Georg S. Ohm, developed this mathematical relationship, which is present in most circuits. This relationship is known as Ohm's law. This relationship states that if the voltage (energy) in a circuit increases, so does the current (flow of charges). If the resistance increases, the current flow decreases.
Voltage (volts) Current (amps) = --------------------------------------------Resistance (ohms, )
To work through this skill sheet, you will need the symbols used to depict circuits in diagrams. The symbols that are most commonly used for circuit diagrams are provided to the right. If a circuit contains more than one battery, the ...view middle of the document...
Calculate the current.
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4. 5. 6. 7. 8. 9. A circuit contains two 1.5 volt batteries and a bulb with a resistance of 3 ohms. Calculate the current. What is the voltage of a circuit with 15 amps of current and toaster with 8 ohms of resistance? A light bulb has a resistance of 4 ohms and a current of 2 A. What is the voltage across the bulb? How much voltage would be necessary to generate 10 amps of current in a circuit that has 5 ohms of resistance? How many ohms of resistance must be present in a circuit that has 120 volts and a current of 10 amps? An alarm clock draws 0.5 A of current when connected to a 120 volt circuit. Calculate its resistance.
10. A portable CD player uses two 1.5 V batteries. If the current in the CD player is 2 A, what is its resistance? 11. You have a large flashlight that takes 4 D-cell batteries. If the current in the flashlight is 2 amps, what is the resistance of the light bulb? (Hint: A D-cell battery has 1.5 volts.) 12. Use the diagram below to answer the following problems.
a. b. c. d.
What is the total voltage in each circuit? How much current would be measured in each circuit if the light bulb has a resistance of 6 ohms? How much current would be measured in each circuit if the light bulb has a resistance of 12 ohms? Is the bulb brighter in circuit A or circuit B? Why?
13. What happens to the current in a circuit if a 1.5-volt battery is removed and is replaced by a 9-volt battery? 14. In your own words, state the relationship between resistance and current in a circuit. 15. In your own words, state the relationship between voltage and current in a circuit. 16. What could you do to a closed circuit consisting of 2 batteries, 2 light bulbs, and a switch to increase the current? Explain your answer. 17. What could you do to a closed circuit consisting of 2 batteries, 2 light bulbs, and a switch to decrease the current? Explain your answer. 18. You have four 1.5 V batteries, a 1 bulb, a 2 bulb, and a 3 bulb. Draw a circuit you could build to create each of the following currents. There may be more than one possible answer for each. a. b. c. d. 1 ampere 2 amperes 3 amperes 6 amperes
In a series circuit, current follows only one path from the positive end of the battery toward the negative end. The total resistance of a series circuit is equal to the sum of the individual resistances. The amount of energy used by a series circuit must equal the energy supplied by the battery. In this way, electrical circuits follow the law of conservation of energy. Understanding these facts will help you solve problems that deal with series circuits. To answer the questions in the practice section, you will have to use Ohm's law. Remember that: Voltage (volts) Current (amps) = -------------------------------------Resistance (ohms) Some questions ask you to calculate a voltage drop. We often say that each resistor (or light bulb) creates a separate...