Lesson page
Lesson 1: Electrical Theory Essentials
Read the lesson, then answer the multiple-choice practice set below. You get instant right or wrong feedback with explanation.
Electrical Theory Japanese Vocabulary
Lesson Content
This lesson builds the base for every later topic. Learn the core words first, then connect them to simple calculations and real wiring situations.
Japanese Key Term
電圧（でんあつ / voltage）
Hiragana
でんあつ
English Meaning
Voltage
Simple Explanation
Voltage is the force that pushes current through a circuit. If you understand voltage, current, and resistance together, most beginner exam questions become easier.
Detailed Explanation
The written exam often asks you to interpret the meaning of voltage, current, and resistance in practical wiring situations. In Japanese construction language, you will often see 電圧（でんあつ / voltage）, 電流（でんりゅう / current）, and 抵抗（ていこう / resistance） in the same question. Learn the English meaning and the Japanese reading together.
Key Vocabulary
- 電圧（でんあつ / voltage）
- 電流（でんりゅう / current）
- 抵抗（ていこう / resistance）
- 電力（でんりょく / power）
Formula
V = I × R
Worked Example
If current is 2 A and resistance is 6 Ω, voltage is 2 × 6 = 12 V.
Exam Tips
When the problem uses voltage, current, and resistance together, write the formula first before inserting numbers.
Common Exam Trap
Do not confuse voltage with current. Voltage is the push; current is the flow.
Site Reality in Japan
On site, electricians often talk about whether a circuit is live, measured, or isolated. The written exam checks whether you understand the meaning behind the numbers.
Practice Question
A circuit has 10 V and 5 Ω. What is the current?
Answer
2 A
Explanation
Use I = V / R. 10 / 5 = 2 A.
1. If each branch has its own switch as shown, what is true?
L ----[SW]----(Lamp)---- N L ----[SW]----(Fan)----- N
Independent switches on separate branches allow independent operation of each load.
2. What is wrong with this common trap diagram?
L ----(Lamp)----[SW]---- N
Switching neutral is a classic trap. Exam logic expects switching on the live side in basic circuits.
3. This style of drawing usually tests your ability to:
L1 ---[Load A]--- N L2 ---[Load B]--- N
Separate branch paths with labeled loads are used to test circuit tracing and assignment accuracy.
4. Why do both L and N pass through the RCD/ELCB block?
L ---[MCB]---[RCD/ELCB]--- Branches N --------------[RCD/ELCB]--- Branches
Leakage devices compare line and neutral current balance; imbalance indicates leakage path.
5. What exam skill does this pair of notations test?
[Single-line] DB -> SW -> Lamp [Multi-line] L -> SW -> Lamp -> N
The candidate must translate between simplified and detailed conductor representations correctly.
6. If Outlet 1 fails open at its load, Outlet 2 is usually:
L ---+---(Outlet 1)
+---(Outlet 2)
N ---+---(Outlet 1/2)
In a parallel branch arrangement, one load open-circuit does not necessarily interrupt other branches.