ISCET DC Circuits Fundamentals Questions and Answers

Question 1

A technician measures a DC circuit with a 12V source and a single 100-ohm resistor. According to Ohm's Law, what is the expected current flowing through the circuit?

Accepted Answer

120 mA

Answer

Ohm's Law states that Current (I) = Voltage (V) / Resistance (R). In this circuit, I = 12V / 100Ω = 0.12A. To convert amperes to milliamperes (mA), multiply by 1000. Therefore, 0.12A * 1000 = 120 mA.

Question 2

In a DC series circuit containing three resistors (R1=10Ω, R2=20Ω, R3=30Ω), what is the total resistance (Rt)?

Accepted Answer

60 Ω

Answer

For resistors connected in series, the total resistance is the sum of the individual resistances. Therefore, Rt = R1 + R2 + R3 = 10Ω + 20Ω + 30Ω = 60Ω.

Question 3

A resistor has the following color bands: Yellow, Violet, Orange, and Gold. What is the nominal resistance and tolerance of this component?

Accepted Answer

47 kΩ ±5%

Answer

The resistor color code is read as follows: Yellow (4), Violet (7), Orange (multiplier of 1,000). This gives a nominal value of 47 x 1,000 = 47,000 ohms, or 47 kΩ. The fourth band, Gold, indicates a tolerance of ±5%.

Question 4

According to Kirchhoff's Voltage Law (KVL), which of the following statements is true for any closed loop in a DC circuit?

Accepted Answer

The algebraic sum of all voltage drops and rises is zero.

Answer

Kirchhoff's Voltage Law (KVL) is based on the conservation of energy and states that the algebraic sum of the potential differences (voltages) around any closed loop or mesh in a circuit must be equal to zero.

Question 5

A technician is troubleshooting a simple DC circuit with a lamp that fails to light up. A multimeter measurement across the power source shows the correct voltage. Which of the following is the MOST likely cause of the problem?

Accepted Answer

An open circuit in the wiring.

Answer

Since the power supply is verified to be working correctly, the most probable fault is a break in the current path, which is an open circuit. An open circuit, such as a broken wire or a blown fuse, would prevent any current from flowing to the lamp. A short would likely trip a protective device, and the problem states the source voltage is correct.

(ISCET) International Society of Certified Electronics Technicians Practice Test

(ISCET) International Society of Certified Electronics Technicians Practice Test

ISCET DC Circuits Fundamentals Questions and Answers