ARCH-P-13: Electromagnetic Induction (Faraday/Lenz Coil Graphs), AC Generators & Transformer Scaling (V_p/V_s = N_p/N_s)

Full 15-Q Timed Drill

Step 1 of 6 • The Core Idea

ARCH-P-13: Why the 140s Classroom Method Fails Under the 90s Clock

Standard Classroom Method (Too Slow)~140s (Blows 90s Clock)

For an ideal transformer,

I_p V_p = I_s V_s \implies \frac{I_s}{I_p} = \frac{N_p}{N_s}

. Thus secondary current is

I_s = 4 \times \frac{200}{4000} = 0.2\text{ A}

. Power dissipated in the cables is

P = I_s^2 R_{\text{cable}} = (0.2)^2 \times 1500 = 60\text{ W}

(~120s).

The Fast ShortcutTarget: 35s (Saves 105s)

Line 1 (Step-Up Steps Down Current):

I_s = I_p \left(\frac{N_p}{N_s}\right) = 4 \times \frac{1}{20} = 0.2\text{ A}

.
**Line 2 (Cable Heating

I_s^2 R_c

):**

P = (0.2)^2 \times 1500 = 60\text{ W}

(25s).

Where Students Lose Time: In 8 past UAT-UK questions (3.43% of Physics), candidates lose 105s by stepping up voltage by n_s/n_p steps down ideal secondary current by n_p/n_s. Instead, apply P2 with Maths 1 skill M3.4.

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