🧲 Chapter 17: Electromagnetism – 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 short questions from Chapter 17 Electromagnetism including electromagnetism, right-hand grip rule, solenoid, electromagnet, magnetic field lines, force on conductor, Fleming's left-hand rule, D.C motor, relay, loudspeaker, Earth's magnetic field, and dynamo effect. 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 17: Electromagnetism
Electromagnetism covers magnetic fields, right-hand grip rule, solenoid, force on conductors, D.C motor, relay, loudspeaker, and Earth's magnetic field.
📝 Short Questions & Answers (PECTAA 2026)
1 Define electromagnetism.
Answer: Electromagnetism is the branch of physics that deals with the interactions between electric and magnetic fields, explaining how moving electric charges create magnetic fields and how magnetic fields exert forces on moving charges.
✅ Electromagnetism: Interactions between electric and magnetic fields.
2 State the right-hand grip rule for finding the direction of the magnetic field around a current-carrying wire.
Answer: According to the Right-Hand Grip Rule: 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.
✅ Thumb = Current direction, Fingers = Magnetic field direction.
3 Define solenoid.
Answer: A solenoid is a coil of wire wound in the shape of a cylinder that generates a magnetic field when current flows through it. The combined effect of all loops of the wire makes the field strong and uniform, like a bar magnet with north and south poles.
✅ Solenoid: A cylindrical coil of wire that acts as a magnet when current flows.
4 What is an electromagnet?
Answer: A solenoid acts as a magnet and can attract or repel a bar magnet. This temporary magnet, powered by electricity, is called an electromagnet.
✅ Electromagnet: A temporary magnet powered by electricity.
5 State the Right-Hand Rule for a solenoid. OR How do you determine the polarity of a solenoid?
Answer: According to this rule: 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 will point towards the north pole of the solenoid.
✅ Curled fingers = Current direction, Thumb = North pole.
6 Define magnetic field lines. What are the properties of magnetic field lines?
Answer: Magnetic field lines are imaginary lines used to visualize the magnetic field. Properties: (i) Always start from north pole and end at south pole. (ii) Always form closed loops. (iii) Tangent at any point gives direction of field. (iv) Never cross each other. (v) Closer lines mean stronger field.
✅ Magnetic field lines: Imaginary lines that show the direction and strength of the magnetic field.
7 What happens when two parallel current-carrying conductors carry current in the same and opposite directions?
Answer: When two parallel conductors carry current in the same direction, they attract each other. When they carry current in opposite directions, they repel each other.
✅ Same direction → Attract, Opposite direction → Repel.
8 What happens when a current-carrying conductor is placed in a magnetic field?
Answer: A force acts on the current-carrying conductor due to the interaction of its magnetic field with the magnetic field of the magnet. The conductor is pushed or pulled depending on the direction of the current.
✅ A force acts on the conductor due to magnetic field interaction.
9 How can the force on a current-carrying conductor be increased?
Answer: The force becomes stronger if: (i) The electric current (I) in the wire increases. (ii) The magnetic field (B) becomes stronger. (iii) The length (L) of the wire inside the magnetic field increases.
✅ Increase I, B, or L to increase force.
10 Write the formula for the force on a current-carrying conductor.
Answer: The magnitude of the force is given by: \(F = ILB \sin \theta\)
✅ \(F = ILB \sin \theta\)
11 State Fleming's Left-Hand Rule.
Answer: Extend the thumb, forefinger, and middle finger of the left hand so that they are at right angles to one another. If the forefinger represents the magnetic field direction and the middle finger shows the current direction, then the thumb will point in the direction of the force acting on the conductor.
✅ Forefinger = Field, Middle finger = Current, Thumb = Force.
12 Define the SI unit of magnetic field.
Answer: The SI unit of magnetic field (also called magnetic flux density) is the tesla (T). One tesla (1 T) is defined as: The magnetic field strength which causes a force of 1 N on a 1 metre length of wire carrying a current of 1 A perpendicular to the magnetic field. \(1 T = 1 N A^{-1} m^{-1}\).
✅ Tesla (T): \(1 T = 1 N A^{-1} m^{-1}\)
13 What happens when a current-carrying coil is placed in a magnetic field?
Answer: When a current-carrying coil is placed in a magnetic field, it experiences a couple of forces that makes the coil rotate.
✅ The coil experiences a couple and rotates.
14 How can the turning effect on a current-carrying coil be made stronger?
Answer: The turning effect on the coil can be made stronger by: (i) Increasing the number of turns of the coil. (ii) Increasing the current flowing through the coil. (iii) Increasing the strength of the magnetic field.
✅ Increase turns, current, or magnetic field strength.
15 What is an electric motor?
Answer: An electric motor is a device that converts electrical energy into mechanical energy. There are two types: Alternating Current (A.C.) motor and Direct Current (D.C.) motor.
✅ Electric motor: Converts electrical energy to mechanical energy.
16 What is the working principle of a D.C. motor?
Answer: A D.C. motor operates using the interaction between a current-carrying coil (armature) and a magnetic field. When the coil is placed in a magnetic field, it experiences forces that cause it to rotate.
✅ D.C. motor: Interaction between current-carrying coil and magnetic field produces rotation.
17 What is a split ring commutator?
Answer: A split ring commutator is a metal ring divided into two halves, each connected to one end of the coil. It reverses the direction of current after every half turn, allowing the coil to rotate continuously.
✅ Split ring commutator: Reverses current direction every half turn.
18 What is the role of a split ring commutator in a D.C. motor?
Answer: The split ring commutator reverses the direction of current in the coil after every half turn, allowing the coil to rotate continuously.
✅ Ensures continuous rotation by reversing current direction.
19 Define relay.
Answer: A relay is an electrical device that uses magnetism to control another circuit. It acts like a bridge between the input and output circuits, allowing a small current to control a larger current.
✅ Relay: Uses magnetism to control another circuit with a small current.
20 What are the main parts of a relay?
Answer: A mechanical relay consists of: (1) Coil and Core: Wound wire around a magnetic core. (2) Armature: A small movable piece. (3) Return Spring: Brings armature back to original position. (4) Moving Contact: Attached to armature, joins or breaks the circuit.
✅ Coil, core, armature, return spring, and moving contact.
21 Explain the working of a relay.
Answer: When switch OFF: No current flows, armature stays in normal position, lamp circuit remains open. When switch ON: Current flows, coil magnetised, pulls armature, closes lamp circuit, lamp glows.
✅ Switch ON → Coil magnetised → Armature pulls → Circuit closes.
22 State the uses of a relay.
Answer: A relay is used to control another circuit by using a small current. It also helps in opening door locks, starting motor cars, and operating heavy machines.
✅ Control circuits, door locks, motor cars, heavy machines.
23 What is a loudspeaker?
Answer: A loudspeaker is a device that uses the magnetic effects of current to convert electrical signals into sound. When an alternating current flows through the coil, it produces a varying magnetic field. This moves the coil and diaphragm back and forth, producing sound waves.
✅ Loudspeaker: Converts electrical signals into sound using magnetic effects.
24 What is Earth's magnetic field?
Answer: Earth's magnetic field is an invisible shield that surrounds the Earth and stretches into space. It protects the Earth from dangerous solar winds and cosmic radiations.
✅ Earth's magnetic field: An invisible shield that protects from solar winds.
25 State two uses of Earth's magnetic field.
Answer: (i) It protects the Earth from harmful solar winds and cosmic radiations. (ii) It helps in navigation by guiding humans and animals.
✅ Protection from solar winds & navigation.
26 What is the origin of Earth's magnetic field?
Answer: Earth's magnetic field is generated by the movement of liquid metal in its core, a process known as the dynamo effect.
✅ Dynamo effect: Movement of liquid metal in Earth's core.
27 What is the dynamo effect?
Answer: The dynamo effect is the process in which the movement of liquid molten iron and nickel in the Earth's outer core creates electric currents that produce the Earth's magnetic field.
✅ Dynamo effect: Movement of molten iron/nickel creates electric currents and magnetic field.
📐 Key Formulas – Electromagnetism
Force on a Conductor: \( F = ILB \sin \theta \)
SI Unit of Magnetic Field: \( 1 T = 1 N A^{-1} m^{-1} \)
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 short questions, always write precise and to-the-point answers. Use key terms like "right-hand grip rule", "solenoid", "Fleming's left-hand rule", and "dynamo effect" 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