DC Theory, Lvl II - 2nd Ed. Lesson 3: How Current Reacts in DC Series Circuits

Decreasing the applied voltage to a circuit would cause the current to increase. Select one: True False

False

Fuses and circuit breakers are connected in parallel with the load and all other components in the circuit. Select one: True False

False

The current in a series circuit becomes smaller after passing through each resistor in series. Select one: True False

False

What is the current in the circuit if the voltage across resistor R1 is 15 volts? (Round the FINAL answer to two decimal places.)

IR1= ER1/ R1 =15/20 =0.75A Answer is 0.75A

Determine the total circuit current, if resistor R2 was to short out. (Round the FINAL answer to two decimal places.)

RT= R1+R2+R3 = 20 + 0 + 65 = 85Ω IT= ET / RT = 200 V / 85 Ω =2.35 A Note: Since 2.35 amps is greater than 2 amps (the fuse rating), the fuse would blow. The correct answer is: 2.35 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.)

RT= R1+R2+R3 =20 + 40 + 65 = 125Ω IT = ET / RT = 200 / 125 = 1.65 A Note: The total current for the circuit is less than the fuse rating; therefore, the fuse will not blow when the circuit is turned on. The correct answer is: 1.6 A

An increase in the total resistance of a circuit would cause a decrease of the total current in that circuit. Select one: True False

True

If the current becomes excessive, the fuse or circuit breaker will ? and disconnect the load from the power source. Select one: a. close b. open c. short d. none of the above

b. open

Which of the following devices may be used to interrupt current flow through a circuit during a short circuit condition? Select one: a. Circuit breaker b. Fuse c. Rheostat d. a. and b. e. a. and c.

d. a. and b.

Which Ohm's Law formula is used to solve for the total current in a series circuit when voltage and resistance are known? Select one: a. IT = ET/ RT b. RT = ET / IT c. IT = RT/ ET d. IT = ET x RT

IT= ET / RT

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 set at midrange (500 ohms). (Round the FINAL answer to four decimal places.)

RT= R1+R2 =250+500 = 750 Ω IT= ET/ RT = 5 / 750 = 0.0067 A or 6.7 mA The correct answer is: 0.0067 A

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. Select one: True False

True

Solve for the total circuit current in the circuit. (Round the FINAL answer to one decimal place.)

IT= ET/RT = 30/60 =0.5A The correct answer is: 0.5 A

Find the value of R2 in the circuit.

RT = ET/ IT = 240/6 =40Ω R2= RT- R1 = 40-25 =15Ω Answer is 15 Ω

Subscripts allow us to communicate precisely about various components of a circuit by identifying each component with a unique label. Select one: True False

True

If the resistance value of the resistor was doubled, what would happen to the circuit current? Click on the image to view a larger version of it. Select one: 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 1/2 times the original current. d. The circuit current would stay the same.

a. Since the current is inversely proportional to the circuit resistance, the new current would be one-half of the old value.

A circuit having only one current path is called a ? circuit. Select one: a. grounded b. parallel c. series d. short

c. series

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 set at maximum value (1,000 ohms). (Round the FINAL answer to three decimal places.)

RT = R1+R2 = 250 + 1000 =1250 Ω IT= ET / RT = 5/1250 = 0.004 A or 4 mA The correct answer is: 0.004 A

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 set at minimum value (0 ohms). (Round the FINAL answer to two decimal places.)

RT= R1+R2 = 250+ 0 = 250 Ω IT= ET/RT =5/250 =0.02 A or 20 mA The correct answer is: 0.02 A