Units 6,7,8 Delmars Standard Textbook of Electricity 1. What is a series circuit? Circuit with only one path 2. How is a fuse or circuit breaker connected in a circuit? Why? In series so all current must flow through it 3. Voltage drop across a resistor is proportional to what two values? Value of current flow and resistance 4. How is the total voltage drop in a series circuit calculated when you know the voltage drop across each individual resistor? Simply add them up 5. How is total resistance in a series circuit calculated when you know the individual resistor values? Simply add them up 6. What statement can be made about current at any point in a series circuit? It is equal to the total current and the current leaving the source 7. What statement can be made about the applied voltage in a series circuit? Applied voltage is equal to the sum of the voltages dropped across the individual resistors 8. What is the formula for finding current in a series circuit when you know the applied voltage and resistance? I = E/R 9. What is the formula for finding the applied voltage in a series circuit when you know the amperage and resistance? E = I x R 10. What is the formula for finding resistance in a series circuit when you know the applied voltage and amperage? R = E/I 11. What is the formula for calculating power dissipated by each resistor? P1 = E1 x I1 12. How is the total power calculated in any circuit? (series, parallel, or combination) PT = P1 + P2 + P3 + P4 13. How is voltage polarity determined in a circuit? Observing the current flow through the circuit 14. Don’t worry too much about voltage dividers!! Unit 7 1. What is a parallel circuit? Circuit with more than one path for the current 2. What is the total current flow in a parallel circuit equal to? Sum of the current through the individual paths 3. What is the voltage drop across any leg of a parallel circuit? Same as the applied voltage 4. Total resistance in a parallel circuit is always less than what value? The resistance of the lowest value 5. What is the effect on total resistance when another path is added in parallel circuit? Lower overall resistance 6. What is the formula for calculating total resistance in a parallel circuit when all the resistors are of equal value? RT = R1/#R (resistor value divided by the number of resistors) 7. What is the product over sum method for calculating resistance in a parallel circuit? RT = R1 x R2/R1 + R2 (only works for 2 resistors) 8. What is the reciprocal formula for calculating resistance in a parallel circuit? 1/RT = 1/R1 + 1/R2 + 1/R3 9. What is the total resistance for a parallel circuit with three 20 ohm resistors? RT = 20/3 = 6.667 ohms 10. What is the total resistance for a parallel circuit with three 50 ohm resistors? RT = 50/3 = 16.667 ohms 11. How much current will flow in the circuit from question 9 if the supply voltage is 120 volts? IT = ET/RT = 120/6.667 = 18 Amps (17.999) 12. How much current will flow in the circuit from question 10 if the supply voltage is 240 volts? IT = ET/RT = 240/16.667 = 14.4 Amps 13. What is the total resistance of a parallel circuit with a 15 ohm, 20 ohm, and a 30 ohm resistor? 6.667 ohms 14. What is the current flow in the circuit in question 13 if the supply voltage is 240 volts? IT = ET/RT =240/6.667 = 35.99 Amps 15. What is the current through each path in question 13 if the voltage is 240? I1 = E1/R1 = 240/15 = 16 Amps I2 = E2/R2 = 240/20 = 12 Amps I3 = E3/R3 = 240/30 = 8 Amps 16. What is the total resistance in a circuit with a 24 ohm and a 36 ohm resistor connected in parallel? RT = R1 x R2/R1 + R2 =14.4 ohms 17. What is the current flow in the circuit for question 16 if the supply voltage is 36 volts? IT = ET/RT = 36/14.4 = 2.5 Amps 18. What is the current through each path in the circuit from question 16? (36 V) I1 = E1/R1 = 36/24 = 1.5 Amps I2 = E2/R2 = 36/36 = 1 Amp Unit 8 1. What is a combination circuit? Circuit containing both series and parallel components 2. What is the proper method to solve unknown values in a combination circuit? Simplify by using series circuit rules to solve the series parts and parallel circuit rules to solve those parts 3. What is the total resistance in a circuit with two 20 ohm resistors in series with each other but in parallel with a 50 ohm resistor? RBranch = R1 + R2 = 20 + 20 = 40 Ohms RT = RBranch x R3/RBranch+R3 =40 x 50/40 + 50 =22.2 Ohms 4. What is the current flow in the circuit for question 3 if the supply voltage is 120 volts? IT = ET/RT = 120/22.2 = 5.4 Amps 5. What is the voltage drop across each resistor and the current through each resistor in the circuit from question 3? IBranch = EBranch/RBranch = 120/40 = 3 Amps so IR1 and IR2 = 3 Amps ER1 and ER2 = 60 Volts as they each drop half E3 = 120 Volts I3 = E3/R3 = 120/50 = 2.4 Amps 6. What is the power used in each part of the circuit for question 3? P1 = E1 x I1 = 60 x 3 = 180 W P2 = P1 = 180 W P3 = E3 x I3 = 120 x 2.4 = 288 W PT = P1 + P2 + P3 = 180 + 180 + 288 = 648 W