Physics•Hard

Faraday's Law

Physics challenge: A circular coil of 200 turns with area 50 cm² is placed perpendicular to a magnetic field. The field changes from 0.5 T to 2.5 T in 0.4 s.

Scenario

You are investigating electromagnetic induction in a lab. A coil is inside a changing magnetic field, and you need to find the induced EMF and predict the direction of induced current.

Scored questions

Question 1

What is the change in magnetic flux ΔΦ through the coil? (A = 50 cm² = 50×10⁻⁴ m²)

Question 2

What is the magnitude of the induced EMF? (N = 200 turns, Δt = 0.4 s)

Question 3

If the magnetic field is increasing into the page, the induced current (viewed from above) flows:

Clockwise (to oppose the increase)Counterclockwise (to oppose the increase)In the direction of the field changeNo current flows — only EMF is induced

Question 4

A transformer has 100 primary turns and 500 secondary turns. If the primary voltage is 120V, what is the secondary voltage?

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