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

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

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

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

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

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

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

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.

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

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

c. series

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.