IST Electrical and Electronic Knowledge 1 — Questions and Answers
Question 1: What is the standard unit of measurement for electrical resistance?
- Ampere
- Volt
- Ohm (Correct answer)
- Watt
Correct answer: Ohm
Electrical resistance is measured in Ohms, named after German physicist Georg Ohm.
Question 2: According to Ohm's Law, if voltage is 120V and resistance is 30 Ohms, what is the current?
- 2 A
- 3 A
- 4 A (Correct answer)
- 5 A
Correct answer: 4 A
Ohm's Law: Current (I) = Voltage (V) ÷ Resistance (R) = 120 ÷ 30 = 4 Amps.
Question 3: What color is the standard neutral wire in US residential and light commercial wiring?
- Black
- Green
- White or gray (Correct answer)
- Red
Correct answer: White or gray
White or gray wires are the standard colors for neutral conductors in US electrical wiring.
Question 4: What device is used to protect an electrical circuit from damage caused by excess current?
- Capacitor
- Transformer
- Fuse or circuit breaker (Correct answer)
- Relay
Correct answer: Fuse or circuit breaker
Fuses and circuit breakers protect circuits by interrupting the flow of current when it exceeds a safe level.
Question 5: What is the purpose of a ground wire in an electrical circuit?
- To carry the main current load
- To provide a safe path for fault current (Correct answer)
- To regulate voltage levels
- To increase circuit resistance
Correct answer: To provide a safe path for fault current
The ground wire provides a safe low-resistance path for fault current, protecting people from electric shock.
Question 6: If two resistors of 10 Ohms each are connected in series, what is the total resistance?
- 5 Ohms
- 10 Ohms
- 20 Ohms (Correct answer)
- 100 Ohms
Correct answer: 20 Ohms
In a series circuit, total resistance equals the sum of individual resistances: 10 + 10 = 20 Ohms.
IST Electrical and Electronic Knowledge 1
What is the standard unit of measurement for electrical resistance?