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NCERT Books for Class 10 Science - Magnetic Effects of Electric Current - Free PDF Download
NCERT Books for Class 10 Science Chapter 13
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FAQs on NCERT Books for Class 10 Science Chapter 13
1. Which topics from Chapter 13, Magnetic Effects of Electric Current, are most frequently asked in the CBSE Class 10 board exams?
Based on previous years' trends for the CBSE Class 10 Science exam, the most important topics from this chapter are:
- Properties of Magnetic Field Lines: Often asked as 1 or 2-mark questions.
- Fleming's Left-Hand and Right-Hand Rules: Application-based questions are very common.
- Electric Motor: A high-weightage topic, usually asked as a 5-mark question covering principle, diagram, working, and the function of split rings.
- Electromagnetic Induction and Electric Generator: Another key topic for 3 or 5-mark questions, focusing on the principle and working.
- Domestic Electric Circuits: Questions on safety devices like fuses, earthing, overloading, and short-circuiting are frequently asked.
2. What types of diagrams are essential to practice from this chapter to score full marks in the exam?
To score well, students must practice drawing neat and correctly labelled diagrams. For the 2025-26 board exam, focus on:
- The pattern of magnetic field lines around a straight current-carrying conductor.
- The magnetic field lines of a circular current-carrying loop.
- The magnetic field pattern of a solenoid behaving like a bar magnet.
- A schematic diagram of a simple electric motor.
- A schematic diagram of an AC/DC electric generator.
These diagrams are often part of 3-mark and 5-mark questions.
3. How is a 5-mark question on the working of an 'Electric Motor' typically structured in the CBSE board exam?
A 5-mark question on the electric motor is usually broken down to test multiple concepts. A typical mark distribution is as follows:
- Principle: 1 mark (Stating that a current-carrying conductor experiences a force when placed in a magnetic field).
- Labelled Diagram: 1.5 marks (Including armature, magnets, split-ring commutator, brushes, and battery).
- Working: 2 marks (Explaining the rotation of the coil for one half-cycle and the reversal of current).
- Function of Split Rings: 0.5 marks (Explaining their role as a commutator to reverse the direction of current).
4. What are some HOTS (High Order Thinking Skills) questions that can be expected from Magnetic Effects of Electric Current?
HOTS questions test the application of concepts. An example of an expected HOTS question for the 2025-26 exam could be:
"A circular metallic loop is placed in a magnetic field with its plane perpendicular to the field. If you rotate the loop about its diameter, will a current be induced? Justify your answer."
Answer: Yes, a current will be induced. As the loop rotates, the magnetic flux (the amount of magnetic field passing through the loop) continuously changes. According to the principle of electromagnetic induction, a change in magnetic flux induces a current in the loop. The direction of this current can be determined using Fleming's Right-Hand Rule.
5. Why don't two magnetic field lines ever intersect each other?
Two magnetic field lines can never intersect because at any given point, the magnetic field has only one direction. The direction of the magnetic field at a point is given by the tangent to the field line at that point. If two lines were to intersect, it would mean that there are two different directions of the magnetic field at the point of intersection, which is physically impossible. This uniqueness of direction is a fundamental property of magnetic fields.
6. What is the key difference in construction between an AC generator and a DC generator?
The key constructional difference lies in the device used to transfer current from the armature coil to the external circuit.
- An AC generator uses two full rings called slip rings. Each ring is connected to one end of the coil, allowing the alternating current to flow to the external circuit without changing its nature.
- A DC generator uses a split-ring commutator. This device reverses the direction of the current every half rotation, ensuring the current in the external circuit flows in only one direction, thus producing a direct current.
7. Why is a fuse wire with a specific rating always connected in series in a domestic circuit?
A fuse wire is a safety device designed to protect appliances from damage due to excessive current. It is connected in series so that the entire current flowing to the appliance must pass through it. The fuse has a low melting point and a specific current rating (e.g., 5 A). If the current exceeds this rating due to overloading or a short circuit, the fuse wire heats up, melts, and breaks the circuit, stopping the flow of current and preventing damage.
8. How is the direction of force on a current-carrying conductor related to the direction of the current and the magnetic field?
The relationship between these three quantities is described by Fleming's Left-Hand Rule. The rule states that if you stretch the thumb, forefinger, and middle finger of your left hand so they are mutually perpendicular:
- The Forefinger points in the direction of the Magnetic Field (B).
- The Middle finger points in the direction of the Current (I).
- The Thumb will then point in the direction of the Force or motion (F) on the conductor.
This principle is crucial for understanding the operation of electric motors.
9. A student claims that a strong magnetic field can increase the speed of a moving electron. Is this claim correct? Justify your answer.
No, the student's claim is incorrect. A magnetic field can only change the direction of a moving charged particle, not its speed or kinetic energy. The magnetic force on a moving charge is always perpendicular to its velocity. According to the principles of work and energy, a force that is always perpendicular to the direction of motion does no work. Since no work is done on the electron, its kinetic energy, and therefore its speed, remains constant.
