2ALevel 2 Electrical Installation

    Your class. Your study space.

    A place for 2A to recap a topic, try a few questions and work through the answers. Open to everyone in the class — no login needed.

    Start a mixed review

    A student-built resource hosted by NeuroForgeDesign. Use alongside your tutor’s materials.

    A manageable session

    15–20 minutes, one step at a time.

    1. 01

      Recap

      Spend 4 minutes with the notes below.

    2. 02

      Practise

      Try five questions. Use a hint if you get stuck.

    3. 03

      Review

      Check the working and choose what to revisit.

    Choose a topic

    Topic 1

    SI units

    Micro, milli, kilo and mega. Get the units ready before calculating.

    Practise si units

    Quick study notes

    Open one topic at a time. These examples use ideal resistor circuits.

    SI units

    µ = one millionth · m = one thousandth · k = one thousand · M = one million.

    Example: 680 µA ÷ 1,000 = 0.68 mA. Divide by 1,000 again to get 0.00068 A.

    Check: Convert backwards to recover the original number. Capital M and lower-case m mean different things.

    Formula transposition

    V = I × R · I = V ÷ R · R = V ÷ I.

    Example: V = IR. Divide both sides by I: V ÷ I = R. With 12 V and 0.5 A, R = 12 ÷ 0.5 = 24 Ω.

    Check: Put the answer back into the original formula: 0.5 × 24 = 12 V.

    Series circuits

    Rₜ = R₁ + R₂ + … The current is the same throughout the circuit.

    Example: 10 Ω + 20 Ω = 30 Ω. Across 12 V, I = 12 ÷ 30 = 0.4 A. The drops are 4 V and 8 V.

    Check: The voltage drops must add to the supply: 4 + 8 = 12 V.

    Parallel circuits

    For two resistors: Rₜ = (R₁ × R₂) ÷ (R₁ + R₂). Each branch has the same voltage.

    Example: 10 Ω and 20 Ω across 12 V carry 1.2 A and 0.6 A. Total current = 1.8 A; total resistance ≈ 6.67 Ω.

    Check: Total resistance must be below the smallest branch resistance. Branch currents add to supply current.

    Protection concepts

    A current rating alone does not tell you a protective device’s operating time.

    Example: A 40 A MCB marking is a current rating. To establish operating time, use the actual current and that device’s time–current curve.

    Check: Keep the device’s actual operating time separate from the maximum time permitted for the circuit.

    Read Schneider Electric’s breaker characteristics guide. Permitted disconnection times depend on the relevant circuit and earthing conditions; refer to your current course guidance.

    Before the next lesson

    Use these self-checks to decide what to practise next.

    • Can I convert the units before putting numbers into a formula?
    • Can I explain what stays the same in series and in parallel?
    • Can I write one specific question to take to my tutor?

    Quiz answers stay in your current session. Share your own working with your tutor when you need help.