Quiz 7 Flashcards
How Current Reacts in DC Circuits
A circuit having only one current path is called a ? circuit.
a. grounded
b. parallel
c. series
d. short
c. series
Subscripts allow us to communicate precisely about various components of a circuit by identifying each component with a unique label.
True or False?
True.
Which Ohm’s Law formula is used to solve for the total current in a series circuit when voltage and resistance are known?
a. Iₜ = Eₜ / Rₜ
b. Rₜ = Eₜ / Iₜ
c. Iₜ = Rₜ / Eₜ
d. Iₜ = Eₜ × Rₜ
a. Iₜ = Eₜ / Rₜ
Since there is only one current path through a series circuit, the same current must flow through every component, so the current in each component is the same.
True or False?
True.
Which of the following devices may be used to interrupt current flow through a circuit during a short circuit condition?
a. Circuit breaker
b. Fuse
C. Rheostat
d. a. and b.
e. a. and c.
d. a. and b.
Fuses and circuit breakers are connected in parallel with the load and all other components in the circuit.
True or False?
False.
Fuses and circuit breakers are connected in series with the load and all other components in the circuit.
If the current becomes excessive, the fuse or circuit breaker will ? and disconnect the load from the power source.
a. close
b. open
c. short
d. none of the above
b. open
The current in a series circuit becomes smaller after passing through each resistor in series.
True or False?
False.
The current in a series circuit is the same at all points in the circuit. The flow of electrons in the circuit cannot distinguish between the total resistance and the value of individual resistors in series.
An increase in the total resistance of a circuit would cause a decrease of the total current in that circuit.
True or False?
True.
Decreasing the applied voltage to a circuit would cause the current to increase.
True or False?
False.
Decreasing the applied voltage to a circuit would cause the current to decrease.
Solve for the total circuit current in the circuit. (Round the FINAL answer to one decimal place.)
Eₜ = 30 V
Rₜ = 60 Ω
Iₜ = x A
0.5 A
Iₜ = Eₜ / Rₜ
= 30 / 60
= 0.5 A
If the resistance value of the resistor was doubled, what would happen to the circuit current?
a. Since the current is inversely proportional to the circuit resistance, the new current would be one-half of the old value.
b. The circuit current would double.
c. The circuit current would increase by 1 ½ times the original current.
d. The circuit current would stay the same.
Since the current is inversely proportional to the circuit resistance, the new current would be one-half of the old value.
Find the value of R2 in the circuit.
Eₜ = 240 V
R₁ = 25 Ω
R₂ = x Ω
Iₜ = 6 A
15 Ω
Rₜ = Eₜ / Iₜ
= 240 / 6
= 40 Ω
R₂ = Rₜ - R₁
= 40 - 25
= 15 Ω
What is the current in the circuit if the voltage across resistor R1 is 15 volts? (Round the FINAL answer to two decimal places.)
Eₜ = x V
R₁ = 20 Ω
R₂ = 60 Ω
Vᴿ¹ = 15 V
Vᴿ² = x V
Iₜ = x A
.75 A
Iᴿ¹ = Eᴿ¹ / R₁
= 15 / 20
= 0.75 A
The circuit is designed so the fuse will limit current in the circuit to 2 amps. If the circuit current exceeds 2 amps, the fuse will blow, opening the circuit. Determine the total current of the circuit to see if the fuse will blow. (Round the FINAL answer to one decimal place.)
Eₜ = 200 V
R₁ = 20 Ω
R₂ = 40 Ω
R₃ = 65 Ω
Iₜ = x A
1.6 A
Rₜ = R₁ + R₂ + R₃
= 20 + 40 + 65
= 125
Iₜ = Eₜ / Rₜ
= 200 V / 125 Ω
= 1.6 A
The total current for the circuit is less than the fuse rating; therefore, the fuse will not blow when the circuit is turned on
Calculate the total circuit current, if resistor R2 was to short out. (Round the FINAL answer to two decimal places.)
Eₜ = 200 V
R₁ = 20 Ω
R₂ = 0 Ω
R₃ = 65 Ω
Iₜ = x A
2.35 A
Rₜ = R₁ + R₂ + R₃
= 20 + 0 + 65
= 125
Iₜ = Eₜ / Rₜ
= 200 V / 85 Ω
= 2.35 A
Since 2.35 amps is greater than 2 amps (the fuse rating), the fuse would blow.
The following circuit contains two resistors. One is a fixed value resistor, but the other is a variable resistor which is being used as a rheostat. Calculate the circuit current with the rheostat (R2) set at minimum value (0 ohms). (Round the FINAL answer to two decimal places.)
Eₜ = 5 V
R₁ = 250 Ω
R₂ = 0 Ω
Iₜ = x A
.02 A
Rₜ = R₁ + R₂
= 250 + 0
= 250 Ω
Iₜ = Eₜ / Rₜ
= 5 / 250
= 0.02 A or 20 mA
The following circuit contains two resistors. One is a fixed value resistor, but the other is a variable resistor which is being used as a rheostat (R2). Calculate the circuit current with the rheostat set at midrange (500 ohms). (Round the FINAL answer to four decimal places.)
Eₜ = 5 V
R₁ = 250 Ω
R₂ = 500 Ω
Iₜ = x A
0.0067 A
Rₜ = R₁ + R₂
= 250 + 500
= 750 Ω
Iₜ = Eₜ / Rₜ
= 5 / 250
= 0.0067 A or 6.7 mA
The following circuit contains two resistors. One is a fixed value resistor, but the other is a variable resistor which is being used as a rheostat (R2). Calculate the circuit current with the rheostat set at maximum value (1,000 ohms). (Round the FINAL answer to three decimal places.)
Eₜ = 5 V
R₁ = 250 Ω
R₂ = 1000 Ω
Iₜ = x A
.004 A
Rₜ = R₁ + R₂
= 250 + 1000
= 1250 Ω
Iₜ = Eₜ / Rₜ
= 5 / 250
= 0.004 A or 4 mA
