📡 Chapter 18: Electromagnetic Induction & EM Waves – Exercise Short Questions
Prepared by Muhammad Tayyab, Subject Specialist Physics, Govt Christian High School Daska. Based on PECTAA 2026 syllabus (National Curriculum 2023).
📖 What's Inside: This section covers exercise short questions from Chapter 18 Electromagnetic Induction & EM Waves including Lenz's Law, slip rings in A.C. generators, zero induced e.m.f., sky colour at sunset, and transformers. Each question is presented with a precise answer as per the official PECTAA 2026 Physics curriculum. Perfect for Punjab Boards (Lahore, Gujranwala, Multan, etc.) and all BISE boards across Pakistan.
📚 Related Resources – Chapter 18
Electromagnetic Induction covers Faraday's law, Lenz's law, A.C. generators, transformers, cathode rays, CRO, and EM waves.
📝 Exercise Short Questions & Answers (PECTAA 2026)
18.1 What is the direction of induced current in Lenz's law?
Answer: According to Lenz's Law, the direction of induced current is always such that it opposes the cause which produces it.
✅ Induced current opposes the cause that produces it.
18.2 Why are slip rings used in an A.C. generator?
Answer: Slip rings are used in an A.C. generator to maintain continuous electrical contact with the rotating coil while allowing current to alternate naturally.
✅ Maintain continuous contact, allow alternating current.
18.3 When is induced e.m.f. zero in an A.C. generator?
Answer: When the coil is vertical, it moves along the field lines, and no magnetic flux is cut. So, the induced voltage (e.m.f.) is zero.
✅ Coil vertical → No flux cut → Zero e.m.f.
18.4 Why is the sky red at sunset?
Answer: During sunrise or sunset, sunlight travels through a longer path in the atmosphere. Much of the blue light is scattered out of the path, while the longer wavelengths, such as red and orange, scatter less. These colours dominate the sky near the horizon, giving it a reddish appearance.
✅ Longer path → Blue light scattered → Red/orange remain.
18.5 What is a transformer and on what principle does it work?
Transformer: A transformer is a device used to increase or decrease the voltage in an alternating current (A.C.) circuit. It works without any electrical connection between its input and output coils.
Principle: A transformer works on the principle of electromagnetic induction. A changing magnetic field produced by the primary coil induces an e.m.f. in the secondary coil.
✅ Transformer: Changes A.C. voltage. Principle: Electromagnetic induction.
📐 Key Formula – Transformer
\(\frac{V_s}{V_p} = \frac{N_s}{N_p}\)
Turns-Ratio Equation
Unit 10Thermal Physics
Unit 11Transfer of Thermal Energy
Unit 12Waves
Unit 13Sound
Unit 14Light
Unit 15Electrostatics
Unit 16Electricity
Unit 17Electromagnetism
Unit 18✨ Electromagnetic Induction & EM Waves
Unit 19Electronics
Unit 20Atomic and Nuclear Physics
Unit 21Space and Environment
📖 Complete syllabus coverage for Class 10 Physics (PECTAA 2026) – Units 10 to 21
💡 Exam Tip:
For exercise short questions, write precise and to-the-point answers. Use key terms like "Lenz's Law", "slip rings", "electromagnetic induction", and "scattering of light" as they are commonly tested in exams. These questions follow the PECTAA 2026 pattern and are prepared by Subject Specialist Muhammad Tayyab.
Created by Hira Science Academy | Aligned with PECTAA 2026 Syllabus