CBSE Class 10 Science Chapter 12 ‘Magnetic Effects of Electric Current’ Notes

Introduction:

Welcome to our online tutorial classes, where learning meets innovation! In this segment, we embark on an exciting journey into the realm of matter with our meticulously crafted CBSE Class 10 Science Chapter 12 notes on “Magnetic Effects of Electric Current”. Through these notes, we aim to ignite your curiosity, deepen your understanding, and empower you with knowledge that transcends the boundaries of the classroom.

This chapter explores the relationship between electricity and magnetism. Key points include magnetic field lines, force on current-carrying conductors, domestic electric circuits, and safety measures. Understanding these concepts is essential for practical applications and safety in electrical systems.

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CBSE Class 10 Science Chapter 12 ‘Magnetic Effects of Electric Current’ Overview

CBSE Class 10 Science Chapter 12: Magnetic Effects of Electric Current explores the fascinating relationship between electricity and magnetism. It covers topics such as magnetic field lines, force on current-carrying conductors, and domestic electric circuits. The accidental discovery by Hans Christian Oersted that an electric current through a metallic wire produces a magnetic effect is highlighted. Students learn about magnetic fields due to straight conductors, circular loops, and solenoids. Safety measures, including electric fuses, are discussed. Understanding these concepts is crucial for practical applications and ensuring safe electrical systems in our daily lives.

With our expertly curated notes, you’ll be well-equipped to ace your CBSE Class 10 Science exams and embark on a lifelong journey of discovery and learning.

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CBSE Class 10 Science Chapter 12 ‘Magnetic Effects of Electric Current’ Notes

Magnet and Magnetic Field:

• A magnet is an object that attracts materials made of iron, cobalt, and nickel.
• When suspended freely, a magnet aligns itself in the North-South direction.
• Magnetic field: The area around a magnet where a magnetic force is experienced is called the magnetic field. It is a vector quantity with both direction and magnitude.
• Magnetic field lines represent the influence of force surrounding a magnet. They emerge from the North pole and merge at the South pole.
• Iron filings arrange themselves along the magnetic field lines when placed around a bar magnet.

Properties of Magnets:

• North pole: The pole of a magnet pointing toward the North direction.
• South pole: The pole of a magnet pointing toward the South direction.
• Like poles repel each other, while unlike poles attract each other.

Strength of Magnetic Field:

• The closeness of field lines indicates the relative strength of the magnetic field.
• Crowded field lines near the poles of a magnet represent stronger magnetic fields.

Oersted’s Experiment:

• Hans Christian Oersted accidentally discovered the relationship between electricity and magnetism in 1820.
• He observed that a compass needle deflected when an electric current passed through a nearby metallic wire.
• This experiment demonstrated that electricity and magnetism are interconnected phenomena.
• Oersted’s research led to technologies such as radio, television, and fiber optics.
• The unit of magnetic field strength is named the oersted in his honor.

Applications of Magnets:

Magnets are used in various applications:

• Refrigerators
• Radio and stereo speakers
• Audio and video cassette players
• Children’s toys
• Hard disks and floppies in computers

Compass Needle and Magnet:

• A compass needle behaves like a small bar magnet.
• The ends of the compass needle point approximately towards the North and South directions.
• The end pointing towards the North is called the north-seeking pole, while the end pointing towards the South is called the south-seeking pole.
• Like poles of magnets repel each other, while unlike poles attract each other.

Observing Magnetic Field with Iron Filings:

Activity 12.2:

• Place a bar magnet in the center of a sheet of white paper fixed on a drawing board.
• Sprinkle iron filings uniformly around the bar magnet.
• Tap the board gently.
• The iron filings arrange themselves in a pattern around the magnet.

• The pattern demonstrates the magnetic field around the magnet.
• The region surrounding a magnet, where the force of the magnet can be detected, is said to have a magnetic field.
• The lines along which the iron filings align represent magnetic field lines.

Drawing Magnetic Field Lines:

Activity 12.3:

• Take a small compass and a bar magnet.
• Place the magnet on a sheet of white paper fixed on a drawing board.
• Mark the boundary of the magnet.
• Place the compass near the North pole of the magnet.
• Observe how the compass needle behaves.
• Mark the position of the two ends of the needle.
• Move the needle step by step until you reach the South pole of the magnet.
• Join the marked points on the paper with a smooth curve. This curve represents a field line.
• Repeat the procedure to draw multiple field lines.

• The direction of the magnetic field is taken to be the direction in which a North pole of the compass needle moves inside it.
• By convention, magnetic field lines emerge from the North pole and merge at the South pole.
• Inside the magnet, the direction of field lines is from its South pole to its North pole (closed curves).
• The relative strength of the magnetic field is indicated by the closeness of the field lines.
• No two field lines cross each other.

Activity 12.4: Determining Magnetic Field Direction

• Take a long straight copper wire, two or three cells of 1.5 V each, and a plug key.
• Connect them in series.
• Place the straight wire parallel to and over a compass needle.
• Observe the direction of deflection of the north pole of the needle:
  • If the current flows from North to South, the compass needle’s north pole moves towards the East.
  • If the current flows from South to North, the compass needle’s north pole moves towards the West.
• The direction of the magnetic field produced by the electric current is also reversed when the current direction changes.

Magnetic Field due to a Current through a Straight Conductor

Activity 12.5:

• Take a battery (12 V), a variable resistance (rheostat), an ammeter (0–5 A), connecting wires, and a long straight thick copper wire.
• Insert the thick wire through the center of a rectangular cardboard (fixed in place).
• Connect the copper wire vertically between points X and Y
• Sprinkle iron filings uniformly on the cardboard.
• Tap the cardboard gently.
• Iron filings align themselves in concentric circles around the copper wire.

• The concentric circles represent magnetic field lines.
• To find the direction of the magnetic field:
  • Place a compass at a point (say P) over a circle.
  • Observe the direction of the needle (north pole).
  • The needle’s direction gives the magnetic field lines produced by the electric current through the straight wire at point P.
• The deflection of the compass needle changes with varying current:
  • Increased current leads to increased deflection.
  • Decreased current results in decreased deflection.
• The magnetic field strength decreases as the distance from the conductor increases.

Right-Hand Thumb Rule

• Imagine holding a current-carrying straight conductor in your right hand:
  • Thumb points in the direction of current.
  • Fingers wrap around the conductor in the direction of the magnetic field lines.
• This rule helps determine the direction of the magnetic field associated with a current-carrying conductor.

Magnetic Field due to a Current through a Circular Loop:

• When a straight wire carrying current is bent into a circular loop, the magnetic field lines around it form concentric circles.
• As we move away from the wire, the circles become larger, and at the center of the loop, they appear as straight lines.
• Each section of the wire contributes to the magnetic field lines in the same direction within the loop.
• For a circular coil with n turns, the magnetic field produced is n times that of a single turn due to the cumulative effect of each turn.

Activity 12.6: Demonstrating Magnetic Field Lines in a Circular Coil:

• Insert a circular coil with many turns through holes in a rectangular cardboard.
• Connect the coil ends in series with a battery, a key, and a rheostat.
• Sprinkle iron filings uniformly on the cardboard.
• Tap the cardboard gently to observe the pattern of iron filings, which represents the magnetic field lines.

Magnetic Field due to a Current in a Solenoid:

• A solenoid is a coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder.
• The magnetic field lines around a current-carrying solenoid are similar to those around a bar magnet.
• Inside the solenoid, the field lines are parallel and uniform.
• A strong magnetic field inside a solenoid can magnetize a piece of magnetic material (like soft iron) placed inside, creating an electromagnet.

Force on a Current-Carrying Conductor in a Magnetic Field:

• When a current-carrying conductor is placed in a magnetic field, it experiences a force.
• The force depends on the direction of current and the magnetic field.
• Andre Marie Ampere suggested that the magnet exerts an equal and opposite force on the conductor.
• Activity 12.7 demonstrates this force using an aluminum rod suspended between the poles of a horseshoe magnet.
• Fleming’s left-hand rule helps determine the direction of the force:

• Stretch your left hand with the thumb, forefinger, and middle finger mutually perpendicular.
• If the first finger points in the direction of the magnetic field and the second finger in the direction of current, the thumb points in the direction of the force on the conductor.

Applications of Current-Carrying Conductors and Magnetic Fields:

• Electric motor
• Electric generator
• Loudspeakers
• Microphones
• Measuring instruments

Main Supply and Wiring in Homes:

• Electric power is supplied to homes through a main supply (mains), either via overhead electric poles or underground cables.
• The main supply consists of two wires:
  • Live wire (positive): Usually insulated with red cover.
  • Neutral wire (negative): Insulated with black cover.
• The potential difference between the live and neutral wires is typically 220 V in our country.
• At the meter-board, these wires pass through an electricity meter and a main fuse.
• The main switch connects them to the line wires within the house.

Separate Circuits in Homes:

• Homes have separate circuits for different appliances:
  • 15 A circuit: Used for appliances with higher power ratings (e.g., geysers, air coolers).
  • 5 A circuit: Used for bulbs, fans, etc.
• Appliances are connected across the live and neutral wires.
• Each appliance has its own switch to control the flow of current.
• To ensure equal potential difference for each appliance, they are connected in parallel.

Earth Wire for Safety:

• The earth wire (insulated with green color) is connected to a metal plate buried deep in the earth near the house.
• Safety measure for appliances with metallic bodies (e.g., electric press, toaster, refrigerator, etc.).
• The metallic body is connected to the earth wire, providing a low-resistance path for current.
• Ensures that any leakage of current to the metallic body keeps its potential equal to that of the earth, preventing severe electric shocks.

Electric Fuse:

• An essential component in domestic circuits.
• Prevents damage to appliances and circuits due to overloading.
• Overloading occurs when the live and neutral wires come into direct contact (e.g., damaged insulation or appliance faults).
• Short-circuiting results from abrupt increases in current.
• The electric fuse melts due to Joule heating, breaking the circuit and preventing damage.
• Overloading can also occur due to accidental voltage hikes or connecting too many appliances to a single socket.

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Engage and Excel

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Join us on this captivating journey as we unravel the mysteries of matter in our surroundings. With our expertly curated notes, you’ll be well-equipped to ace your CBSE Class 10 Science exams and embark on a lifelong journey of discovery and learning.

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