N-Level Technical and Vocational Skills 2 — Questions and Answers
Question 1: What is the difference between AC and DC electricity?
- AC is from batteries; DC is from power sockets
- AC (alternating current) periodically reverses direction; DC (direct current) flows in one direction only (Correct answer)
- DC is more dangerous than AC
- AC is used in torches; DC in homes
Correct answer: AC (alternating current) periodically reverses direction; DC (direct current) flows in one direction only
AC (mains electricity in Singapore — 230V, 50Hz) alternates direction. DC (batteries, electronic devices) flows in one constant direction. Most household appliances use AC; electronics convert it to DC internally.
Question 2: What does a fuse do in an electrical circuit?
- Increases the current
- Protects the circuit by melting and breaking the circuit if the current exceeds the safe rating (Correct answer)
- Stores electrical energy
- Measures voltage
Correct answer: Protects the circuit by melting and breaking the circuit if the current exceeds the safe rating
A fuse is a safety device containing a thin wire that melts and breaks the circuit if the current exceeds its rated value, preventing damage to equipment and reducing fire risk.
Question 3: What is the function of a resistor in an electronic circuit?
- To store charge
- To limit or control the flow of electric current (Correct answer)
- To amplify signals
- To convert AC to DC
Correct answer: To limit or control the flow of electric current
A resistor limits current flow in a circuit. By Ohm's Law (V = IR), adding resistance reduces current for a given voltage, protecting sensitive components from too much current.
Question 4: What is 'Computer-Aided Design' (CAD)?
- Drawing designs by hand on paper
- Using computer software to create, modify, and analyse design drawings — allowing precise, editable technical drawings (Correct answer)
- Typing a description of a product
- A type of computer game for designers
Correct answer: Using computer software to create, modify, and analyse design drawings — allowing precise, editable technical drawings
CAD software (e.g., AutoCAD, SolidWorks) allows designers and engineers to create precise 2D and 3D digital drawings that can be easily modified, shared, and used for manufacturing.
Question 5: In a food preparation environment, what does HACCP stand for and why is it important?
- Hot And Cold Cooking Principles — to ensure good flavour
- Hazard Analysis and Critical Control Points — a food safety system identifying risks in food production to prevent contamination (Correct answer)
- Hygiene And Cleanliness Control Programme — for restaurant decoration
- Health And Calorie Control Plan — for dieting
Correct answer: Hazard Analysis and Critical Control Points — a food safety system identifying risks in food production to prevent contamination
HACCP is a systematic food safety approach that identifies, evaluates, and controls biological, chemical, and physical hazards at critical points in food production to prevent foodborne illness.
Question 6: What is the purpose of earthing (grounding) in electrical installations?
- To increase the power supply
- To provide a safe path for fault current to flow to the ground, preventing electric shock and fire (Correct answer)
- To improve the quality of electricity
- To reduce electricity consumption
Correct answer: To provide a safe path for fault current to flow to the ground, preventing electric shock and fire
Earthing connects metallic parts of electrical appliances to the ground. If a fault occurs and live voltage reaches the casing, the earth wire safely conducts the current away, preventing electric shock.
N-Level Technical and Vocational Skills 2
What is the difference between AC and DC electricity?