AFCT Electronics Information 2 — Questions and Answers
Question 1: What is the unit of measurement for electrical resistance?
- Ampere
- Ohm (Correct answer)
- Volt
- Watt
Correct answer: Ohm
The ohm is the SI unit of electrical resistance, named after German physicist Georg Simon Ohm.
The ohm measures electrical resistance, the opposition to current flow in a circuit. One ohm is defined as the resistance that produces a potential difference of one volt when a current of one ampere flows through it. Ohm's Law (V = IR) relates voltage, current, and resistance.
Question 2: In a series circuit with three resistors of 10, 20, and 30 ohms, what is the total resistance?
- 5.45 ohms
- 60 ohms (Correct answer)
- 20 ohms
- 6 ohms
Correct answer: 60 ohms
In a series circuit, total resistance is the sum of all individual resistances: 10 + 20 + 30 = 60 ohms.
In a series circuit, current must flow through each resistor in sequence, so the total resistance is the sum: R_total = R1 + R2 + R3 = 10 + 20 + 30 = 60 ohms. This is different from parallel circuits where the reciprocal formula is used.
Question 3: What component in a circuit allows current to flow in only one direction?
- Resistor
- Diode (Correct answer)
- Capacitor
- Inductor
Correct answer: Diode
A diode is a semiconductor device that allows current to flow in one direction and blocks it in the opposite direction.
A diode is made of semiconductor material with a P-N junction. When forward-biased, current flows freely. When reverse-biased, the diode blocks current flow. LEDs are a common type that emit light when forward-biased. Diodes are essential in rectifier circuits that convert AC to DC power.
Question 4: What does AC stand for in electrical terminology?
- Accumulated Current
- Alternating Current (Correct answer)
- Applied Charge
- Automatic Circuit
Correct answer: Alternating Current
AC stands for Alternating Current, where the flow of electric charge periodically reverses direction.
Alternating Current (AC) reverses direction periodically. In the United States, standard household AC operates at 60 Hz at 120 volts. AC is preferred for power transmission because it can be easily transformed to higher voltages for efficient long-distance transmission.
Question 5: What happens to the brightness of bulbs connected in series when one bulb burns out?
- Remaining bulbs get brighter
- All bulbs go out (Correct answer)
- Remaining bulbs are unaffected
- Only adjacent bulbs go out
Correct answer: All bulbs go out
In a series circuit, all components share a single current path. If one bulb burns out, the circuit is broken and all bulbs go out.
In a series circuit, there is only one path for current. All components are connected end-to-end. When one bulb burns out, it creates an open circuit. Since no current can flow through the broken link, all other bulbs also go out.
Question 6: What is the purpose of a fuse in an electrical circuit?
- To increase voltage
- To protect against overcurrent (Correct answer)
- To store electrical energy
- To convert AC to DC
Correct answer: To protect against overcurrent
A fuse protects a circuit by melting and breaking the circuit when current exceeds a safe level.
A fuse contains a thin wire or metal strip that melts when excessive current flows through it, breaking the circuit. This protects wiring and equipment from damage caused by overcurrent conditions. Fuses are rated by their maximum current capacity. Once blown, a fuse must be replaced.
AFCT Electronics Information 2
What is the unit of measurement for electrical resistance?