Download Answers Units 6,7,8 Delmars Standard Textbook of Electricity

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