Physics · Grades 11–12
Average induced emf
Use flux change per turn; the question asks magnitude, not the direction set by Lenz’s law.
Rule and assumptions
Use flux change per turn; the question asks magnitude, not the direction set by Lenz’s law.
|ε̄| = N|ΔΦ|/Δt
Worked examples
A 790-turn coil has flux change 2 mWb per turn over 400 ms. Find average induced emf magnitude. Round to 3 decimal places if needed. Answer in V.
|ε̄| = N|ΔΦ|/Δt 790 × (2/1000) / (400/1000) = 3.95
3.95 V
A 470-turn coil has flux change 21 mWb per turn over 80 ms. Find average induced emf magnitude. Round to 3 decimal places if needed. Answer in V.
|ε̄| = N|ΔΦ|/Δt 470 × (21/1000) / (80/1000) = 123.375
123.375 V
Try two questions
A 90-turn coil has flux change 39 mWb per turn over 360 ms. Find average induced emf magnitude. Round to 3 decimal places if needed. Answer in V.
A 210-turn coil has flux change 24 mWb per turn over 420 ms. Find average induced emf magnitude. Round to 3 decimal places if needed. Answer in V.
Answers and reasoning
Answers and marking notes
- 9.75 V
|ε̄| = N|ΔΦ|/Δt 90 × (39/1000) / (360/1000) = 9.75
- 12 V
|ε̄| = N|ΔΦ|/Δt 210 × (24/1000) / (420/1000) = 12
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Learning preview · independent educational and translation review required. Suggested grades are not official curriculum alignment.