🧲 Chapter 17: Electromagnetism – Long 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 long questions from Chapter 17 Electromagnetism including magnetic field creation and its factors, right-hand grip rule for straight wire and solenoid, Oersted's experiment with compass and iron filings, and the theory of Earth's magnetic field with the dynamo effect and role of molten core. Each question is presented with a detailed 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 17: Electromagnetism
Electromagnetism covers magnetic fields, right-hand grip rule, force on conductors, D.C motor, relay, loudspeaker, and Earth's magnetic field.
📝 Long Questions & Answers (PECTAA 2026)
17.1 How is a magnetic field created around a current-carrying wire, and what factors affect its strength?
Answer: A steady electric current in a conductor generates a magnetic field (B) around it because moving electric charges create magnetic fields. The magnetic field forms concentric circles around the current-carrying conductor.
Factors affecting its strength:
- Electric current (I): Increasing the current produces a stronger magnetic field.
- Distance from the conductor: The magnetic field is strongest near the conductor and weakens with distance.
- Number of wire loops (solenoid): Winding the wire into a solenoid combines the effect of all loops, making the magnetic field stronger and more uniform.
✅ Magnetic field forms concentric circles; strength depends on current, distance, and number of loops.
17.2 Explain the concept of the right-hand grip rule and how it helps determine the direction of the magnetic field around a current-carrying conductor.
Concept: The right-hand grip rule is a simple method that helps us to quickly find the direction of the magnetic field around a current-carrying conductor. The magnetic field forms circular loops around the wire, and its direction depends on the direction of the current. If the current changes direction, the direction of the magnetic field also changes.
Rule for a Straight Wire:
If you hold the wire in your right hand with your thumb pointing in the direction of the current, then your fingers curl around the wire in the direction of the magnetic field.
Rule for a Solenoid:
If you grip the solenoid with your right hand such that the curled fingers point in the direction of the conventional current, then the thumb points towards the north pole of the solenoid.
✅ Thumb = Current direction, Fingers = Magnetic field direction (straight wire); Curled fingers = Current, Thumb = North pole (solenoid).
17.3 Describe an experiment that demonstrates the magnetic field produced by a current-carrying conductor using a compass or iron filings.
Experiment:
Hans Christian Oersted stated that a steady electric current in a conductor generates a magnetic field B around it. This can be demonstrated by passing a current-carrying wire through a vertical cardboard sheet and connecting it to a battery. When current flows, a magnetic field is produced around it.
Observation:
Concentric circles are formed by the magnetic field around the conductor. This can be observed by placing small compasses or sprinkling iron filings on the cardboard. The compass needles align themselves along the direction of the magnetic field, pointing tangentially to the circular lines of force.
If the direction of the current is reversed by switching the battery terminals, the compass needles and iron filings also reverse their alignment, indicating that the magnetic field direction depends on the current flow.
✅ Oersted's experiment: Current-carrying wire produces a magnetic field with concentric circles; reversing current reverses field direction.
17.4 Discuss the theory behind the Earth's magnetic field and the role of the Earth's molten core in generating it.
Origin of Earth's Magnetic Field:
The Earth acts like a giant magnet. Scientists believe this is because its molten iron core is constantly spinning and the movement of these charged particles creates a huge magnetic field. Earth's magnetic field is thought to be generated by the movement of liquid metal in its core, a process known as the dynamo effect.
Role of the Molten Core:
The core has two parts: a solid inner core and a liquid outer core made of molten iron and nickel. As the Earth spins, heat from the inner core causes the liquid metal to flow, creating electric currents. These currents produce magnetic fields, which combine and grow stronger due to the Earth's rotation. This process, called magneto-hydrodynamics, keeps the magnetic field active and forms the magnetosphere, a protective barrier that shields Earth from harmful solar wind and space radiation.
✅ Dynamo effect: Movement of molten iron/nickel in Earth's core generates electric currents, producing the magnetic field and forming the magnetosphere.
🧲 Key Concepts – Electromagnetism
Magnetic Field: \( B \) is created by moving charges (current).
Right-Hand Grip Rule (Straight Wire): Thumb = Current, Fingers = Magnetic field.
Right-Hand Grip Rule (Solenoid): Curled fingers = Current, Thumb = North pole.
Dynamo Effect: Movement of liquid metal in Earth's core generates electric currents and magnetic field.
Unit 10Thermal Physics
Unit 11Transfer of Thermal Energy
Unit 12Waves
Unit 13Sound
Unit 14Light
Unit 15Electrostatics
Unit 16Electricity
Unit 17✨ Electromagnetism
Unit 18Electromagnetic 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 long questions, write detailed answers with clear headings, bullet points, and explanations. Use key terms like "concentric circles", "right-hand grip rule", "dynamo effect", and "magneto-hydrodynamics" 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