Name: SIMPLE DC WORKSHEET OUTLINE: 1. Overview of Ohm's law 2. Introduction to the circuit symbol 3. Electrical quantities and units 4. Series and Parallel Circuits and characteristics 5. Example problems OHM'S LAW Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. In equation form, V = 1 x R, where V is voltage, I is current, and R is resistance. CIRCUIT SYMBOLS These are the most commonly used symbols in circuit diagramming. ELECTRICAL QUANTITIES AND UNITS Voltage (AV) is the difference in electric potential between two points. It is also the work needed per unit charge to move a test charge between two points. It is measured in Current (1) is the stream of charged particles, such as electrons, moving through an electrical conductor or space. It is measured in Amperes or Amps (A). Resistance (R ) is the meas position to the flow of electric current. It is measured in Ohms, or Q. SERIES AND PARALLEL CIRCUITS AND CHARACTERISTICS Resistors in Series Characteristics Anytime that we have more than one resistor in a row, the configuration is described as having resistors in series. See the figure below. age 1 of 4 . The same current flows through each resistor. . Potential difference is distributed among the resistors. The resistor with the biggest resistance has the greatest voltage. The total resistance is equal to the sum of all the circuit resistance and is always more than any resistor in the configuration. . If one resistor is faulty, the circuit will not work. Resistors in Parallel Characteristics Another possible way to arrange resistors in a circuit is to have multiple resistors branch off from a single junction. See the figure below. In a parallel circuit, there are multiple paths for current flow. The current is distributed among the resistors in each branch. . Potential difference is the same across all resistors in parallel The smallest resistan . The equivalent resistance is always less than any resistor in the configuration. . If one resistor is faulty, the circuit will still work. EXAMPLE PROBLEMS Example 1: An electronic device has a resistance of 20 ohms and a current of 15 A. What is the voltage across the device? Solution: Resistance, current, and voltage are related together by Ohm's law as V=IR. Thus, the voltage of the device is obtained as V=/R=15 Ax20 ohms=300V Example 2: What is the current passing through a 1.4kQ resistor when the voltage across it is 280 V? Solution: Using Ohm's law, V=I R, we have I = V/R=(280 V)/ (1.4x1000 0)=0.2 A Example 3: Find the resista he circus asures a 0.25 A current in Solution: Using Ohm's law, V=I R, we have R = V/1=(30 V)/ (0.25 A)=120 ohms age 2 of 4 ACTIVITY PART 1. Refer to the two circuits below . 5 v dry cell- Circuit A Circuit B 1. Which shows light bulbs or resistors in series? _ in parallel?_ 2. In A, what happens if one light bulb is not working? 3. In B, what happens if one light bulb is not working? What about in B? 1. Assuming that all light bulbs are similar, what can you say about the current in each of the bulbs in circuit A? . If the light bulbs in A were all different, what can you say about the current in each of the bulbs ? . How would you compare the total current in circuit A with the current in the first light bulb? The second light bulb? Page 3 of 4 7. Assuming that all light bulbs are similar, what can you say about the current in each of the bulbs in circuit B? 8. If the light bulbs in B were all different, what can you say about the current in each of the bulbs? . How would you compare the total current in circuit B with the current in the first light bulb? The second light bulb? 10. Give an example of a circuit similar to A, and similar to B. ACTIVITY PART 2. USE OHM'S LAW, V - 1 X R TO SOLVE THESE PROBLEMS. SHOW YOUR WORK. 11. What is the voltage if a resistance of 25 0 produces a current of 250 amperes? 12. What is the current produced by a voltage of 240 V through a resistance of 0.2 0? 13. What voltage is necessary to produce a current of 200 A through a resistance of 100 n? 14. What resistance would produce a current of 120 amps from a 6-V battery? 15. What is the current produced by a 9-V battery flowing through a resistance of 200 0? age 4 of 4