Module 2 Units 1,2,3,4
1. What is a series circuit? Circuit with only one path for current
2. What is the result of an open anywhere in a series circuit? No current flows
3. Why is it important to identify polarity when measuring amperage or voltage in a
DC circuit? Meter may be damaged
4. What is the formula for calculating total resistance in a series circuit? RT = R1 +
R2 + R3 + R4
5. What statement describes the amperage through each part of a series circuit?
Amperage through any part of a series circuit is the same. IT = I1 = I2 = I3 = I4
6. What value determines the amount of voltage dropped across each resistor in a
series circuit? Value in ohms
7. What is the formula for calculating total voltage in a series circuit? ET = E1 + E2 +
E3 + E4
8. What is the formula to calculate voltage drop across each resistor? E1= I1x R1
9. What voltage is measured across any open in a series circuit? Supply voltage
10. What is the voltage drop across a 15 ohm and a 20 ohm resistor connected in
series to a 120 volt supply? RT = R1 + R2 = 15 +20 = 35 ohms IT = ET/RT =
120/35 = 3.42 Amps E1 = I1 x R1 = 3.42 x 15 = 51.3 Volts E2 = I2 x R2 = 3.42 x
20 = 68.4 Volts
11. What is the voltage drop across a 60 ohm and a 90 ohm resistor connected in
series to a 120 volt supply? RT = R1 + R2 = 60 +90 = 150 ohms IT = ET/RT =
120/150 = .8 Amps E1 = I1 x R1 = .8 x 60 = 48 Volts E2 = I2 x R2 = .8 x 90 = 72
Volts
12. What is the voltage drop across a 3 ohm and a 12 ohm resistor connected in series
to a 240 volt supply? RT = R1 + R2 = 3 + 12 = 15 ohms IT = ET/RT = 240/15 = 16
Amps E1 = I1 x R1 = 16 x 3 = 48 Volts E2 = I2 x R2 = 16 x 12 = 192 Volts
13. What is the formula for calculating total power in a series circuit? PT = P1+ P2 +
P3 + P4
14. What is the relationship between the voltage drop across a resistor and the
resistance of that resistor? Proportional
15. What is the first step in solving a word problem describing a circuit? Draw a
diagram
16. What is one method of compensating for line loss? Increase the size of the
conductors
17. What is the difference between line drop and line loss? Line drop is in volts but
line loss is in watts
18. What is the effect of connecting voltage sources in series maintaining proper
polarity? Increased voltage
Unit 2
1. What is the most common type of circuit encountered by electricians? Parallel
2. What value in a parallel circuit is the same across each load? (E, I, or R)
3. What is the definition of a parallel circuit? More than one path for the current
4. What is the relationship between the current through the resistors and the total
current in a parallel circuit? IT = I1 + I2 + I3 + I4
5. What is the relationship between current and resistance in any circuit? Inversely
proportional (As one increases, the other decreases)
6. What is the effect on total resistance in a parallel circuit when an extra path (load)
is added? Less resistance as there are more paths
7. What is the total resistance in a parallel circuit when the values are 5Ω, 10Ω, and
20Ω? 2.86 Ω
8. What are the three formulas for calculating power dissipated in a resistor? P = E x
I, P = I2R, or P = E2/R
9. What is the formula for calculating total power in a parallel circuit when you
know the power used by each resistor? PT = P1+ P2 + P3 + P4
10. What is Kirchoff’s current law? The sum of currents entering a junction must
equal the sum of currents leaving that junction
11. Are word problems or diagrams typically easier to understand? (solving circuits)
12. Total resistance in a parallel circuit is always more than the resistance of the
smallest value. True or False?
13. What is the reciprocal method for calculating total resistance in a parallel circuit?
1/RT = 1/R1 + 1/R2 + 1/R3 + 1/R4
14. What is the product-sum method for calculating total resistance in a parallel
circuit? RT = R1 x R2/R1 + R2 (Only works for 2 resistors)
15. What is the formula for calculating the total resistance for equal resistors in
parallel? RT = R1 / #R
16. What is the advantage of connecting power sources in series? Increase voltage
17. What is the advantage of connecting power sources in parallel? Increase
amperage
18. What are the two most important factors when connecting power sources in
parallel or series? Same terminal voltage and correct polarity
19. What is the result of connecting a jumper across two points of different polarity
on voltage sources? Short circuit
Unit 3
1. How do you solve a combination circuit for total resistance? Break it down into
series and parallel components
2. What is the total resistance in a circuit with a 5Ω and 20 Ω resistor in parallel with
each other and in series with two more 4 Ω (in series with each other) resistors?
(Draw diagram) (Calculate the parallel part) RT = R1 x R2/R1 + R2 = 4 Ω Now
we have three resistors in series so RT = R1 + R2 + R3 = 12 Ω
3. If the circuit above is connected to a 120V source, what is IT? IT = ET/RT = 120 /
12 = 10 Amps
4. What is the total resistance in a circuit with a 6 Ω and 10 Ω resistor in parallel
with each other and in series with a 12 Ω resistor? (Draw diagram) (Calculate the
parallel part) RT = R1 x R2/R1 + R2 = 3.75 Ω Now we have two resistors in series
so RT = R1 + R2 = 3.75 + 12 = 15.75Ω
5. If the circuit above is connected to a 120V source, what is IT? IT = ET/RT = 120 /
15.75 = 7.61 Amps
6.
7. What is the total resistance in a circuit with a 15Ω and 20 Ω resistor in parallel
with each other and in series with two more 10 Ω (in parallel with each other)
resistors? (Draw diagram) (Calculate the parallel part) RT = R1 x R2/R1 + R2 =
8.57 Ω Now we have three resistors in series so RT = R1 + R2 + R3 = 8.57 + 10
+10 = 28.57Ω
8. If the circuit above is connected to a 120V source, what is IT? IT = ET/RT = 120 /
28.57 = 4.2 Amps
9. Don’t worry too much about the really complicated circuits in the module!!
Unit 4
1. What is the purpose of a voltage divider circuit? Get several values of voltage
from a common supply
2. What value will determine the voltage drops in each portion of a voltage divider
circuit? Individual values of resistance
3. What is a potentiometer? Variable resistor with three terminals
4. Work through the self tests and check your answers. If you have a problem, let me
know.