NCERT Science Notes - Class 10
Chapter 12 - Magnetic Effects of Electric Current

Welcome to AJs Chalo Seekhen. This webpage is dedicated to Class 10 | Science | Chapter - 12 | Magnetic Effects of Electric Current. In this chapter, students dive into the intriguing relationship between electricity and magnetism. It explores how electric current can produce a magnetic field and covers the right-hand thumb rule to determine the direction of this field. The chapter also explains electromagnets and their applications, the workings of electric motors, and the significance of electromagnetic induction, including Faraday’s law. This chapter helps students understand the foundational principles behind many electrical devices and technologies we use every day.

NCERT Science Notes - Class 8 Chapter 9 - Friction notes ajs, cbse notes class 10 ajslearning, cbse notes ajs, ajs notes class 10, ajslearning, ajs chalo seekhen

1. Heating Effects of Electric Current:
   • Previously discussed in the chapter on electricity.
2. Magnetic Effects of Electric Current:
   • An electric current-carrying wire behaves like a magnet.
   • Connection between electricity and magnetism.

Activity 12.1: Demonstrating Magnetic Effects

• Materials Needed: Straight thick copper wire, compass, electric circuit setup.
• Procedure:
  • Place the copper wire (XY) between points X and Y in the circuit, ensuring it is perpendicular to the paper.
  • Position a small compass near the wire.
  • Insert the key into the plug to pass current through the circuit.
  • Observe the compass needle.
• Observation:
  • The compass needle deflects when the current flows through the copper wire.
  • Conclusion: The deflection indicates that the electric current produces a magnetic effect, linking electricity and magnetism.

1. Electromagnetism:
   • This chapter will cover:
     • Magnetic fields.
     • Electromagnetic effects.
     • Electromagnets, which utilize the magnetic effect of electric current.

Hans Christian Oersted (1777–1851)

• Contribution:
  • Discovered in 1820 that a compass needle deflects when an electric current passes through a nearby metallic wire.
  • Demonstrated the relationship between electricity and magnetism.
  • His research led to technologies like radio, television, and fiber optics.
• Honor:
  • The unit of magnetic field strength is named the oersted in his honor.

12.1 - Magnetic Field and Field Lines

1. Compass Needle:
   • A compass needle is a small bar magnet.
   • Ends of the compass needle point approximately towards the north and south.
     • North Seeking Pole: Points towards the north.
     • South Seeking Pole: Points towards the south.
   • Magnetic Interaction:
     • Like poles repel each other.
     • Unlike poles attract each other.

Activity 12.2: Observing Magnetic Field Lines

• Materials Needed: White paper, bar magnet, iron filings, adhesive material, and a salt-sprinkler.
• Procedure:
  • Fix a sheet of white paper on a drawing board.
  • Place a bar magnet in the center of the paper.
  • Sprinkle iron filings uniformly around the magnet.
  • Gently tap the board.
• Observation:
  • The iron filings arrange themselves in a specific pattern around the bar magnet.
• Conclusion:
  • The pattern formed by the iron filings demonstrates the influence of the magnet in the surrounding region.
  • The area around a magnet where its force can be detected is called the magnetic field.
  • The lines along which the iron filings align represent magnetic field lines.

1. Drawing Magnetic Field Lines:
   • It is possible to manually draw the magnetic field lines around a bar magnet using the observed patterns.

Activity 12.3: Observing Magnetic Field Lines

1. Materials Needed:
   • Small compass
   • Bar magnet
   • White paper
   • Adhesive material
2. Procedure:
   • Fix a sheet of white paper on a drawing board.
   • Place the bar magnet on the paper and mark its boundary.
   • Position the compass near the north pole of the magnet.
     • Observation: The south pole of the compass needle points towards the north pole of the magnet, while the north pole of the compass needle points away from it.
   • Mark the positions of the two ends of the needle.
   • Move the compass needle so that its south pole takes the position of the north pole.
   • Continue this process step-by-step until reaching the south pole of the magnet.
   • Join the marked points with a smooth curve; this curve represents a field line.
   • Repeat the process to draw multiple lines, illustrating the magnetic field around the magnet.
3. Deflection Observations:
   • As the compass needle is moved along a field line, the deflection increases as it approaches the poles of the magnet.

Current and Magnetic Field Interaction

1. Effect of Current on Magnetic Field:
   • When the current in a copper wire is changed, the deflection of the compass needle also changes.
     • Observation: Increasing the current results in increased deflection of the needle, indicating that the magnetic field strength increases with current.
2. Effect of Distance on Magnetic Field:
   • If the compass is moved away from the wire (while keeping the current constant), the deflection of the needle decreases.
     • Observation: The magnetic field produced by the current decreases as the distance from the wire increases.
     • The concentric circles representing the magnetic field around a current-carrying straight wire become larger as distance increases.

12.2.2 - Right-Hand Thumb Rule

1. Definition: The right-hand thumb rule is a method for determining the direction of the magnetic field around a current-carrying conductor.
2. Procedure:
   • Hold the current-carrying straight conductor with your right hand.
   • Point your thumb in the direction of the current.
   • Your fingers will curl around the conductor in the direction of the magnetic field lines.

Example 12.1: Direction of Magnetic Field

• Given: Current flows through a horizontal power line from east to west.
• To Find: Direction of the magnetic field at a point directly below and directly above the wire.
• Solution:
  • Using the right-hand thumb rule:
    • Below the Wire: The magnetic field turns clockwise when viewed from the east end.
    • Above the Wire: The magnetic field turns anti-clockwise when viewed from the west end.

12.2.3 - Magnetic Field due to a Current through a Circular Loop

1. Magnetic Field Lines Around a Circular Loop:
   • When a straight wire is bent into a circular loop and current flows through it, the magnetic field lines produced resemble concentric circles around the loop.
   • As we move away from the wire, the circles representing the magnetic field increase in size.
2. Magnetic Field at the Center:
   • At the center of the circular loop, the arcs of the concentric circles appear as straight lines.
   • Each point on the wire contributes to the magnetic field lines, all directed similarly within the loop.
3. Direction of Magnetic Field:
   • By applying the right-hand rule, one can determine that every section of the wire contributes to the magnetic field lines in the same direction inside the loop.
4. Effect of Number of Turns:
   • The magnetic field produced by a circular coil is directly proportional to the current and the number of turns $n$n in the coil.
   • If there are $n$n turns in the coil, the magnetic field strength is $n$n times greater than that produced by a single turn because the magnetic fields from each turn add up constructively.

Activity 12.6: Observing Magnetic Field Lines

Materials Needed:

• Rectangular cardboard with two holes
• Circular coil with a large number of turns
• Battery
• Key
• Rheostat
• Iron filings

1. Insert the circular coil through the holes in the cardboard, ensuring it is normal (perpendicular) to the plane of the cardboard.
2. Connect the ends of the coil in series with the battery, key, and rheostat.
3. Sprinkle iron filings uniformly on the cardboard.
4. Plug in the key to allow current to flow through the coil.
5. Gently tap the cardboard a few times to facilitate the alignment of the iron filings.

• After tapping, observe the pattern of the iron filings that emerge on the cardboard, which visually represents the magnetic field lines around the current-carrying circular loop.

12.2.4 - Magnetic Field due to a Current in a Solenoid

1. Definition of Solenoid:
   • A solenoid is a coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder.
2. Magnetic Field Lines:
   • The pattern of magnetic field lines around a current-carrying solenoid resembles that of a bar magnet.
   • One end of the solenoid acts as a magnetic north pole, while the other end behaves as a south pole.
3. Uniform Magnetic Field:
   • Inside the solenoid, the magnetic field lines are parallel and straight, indicating that the magnetic field is uniform throughout the interior.
   • This uniformity means that the magnetic field strength is the same at all points inside the solenoid.
4. Electromagnet Formation:
   • A strong magnetic field produced inside a solenoid can magnetize a piece of magnetic material (e.g., soft iron) placed within the coil.
   • The magnet formed in this way is referred to as an electromagnet.

12.3 - FORCE ON A CURRENT-CARRYING CONDUCTOR 

IN A MAGNETIC FIELD

1. Concept of Force on a Conductor:
   • An electric current flowing through a conductor generates a magnetic field. When this conductor is placed in an external magnetic field, it experiences a force.
   • French scientist André-Marie Ampère proposed that a magnet exerts an equal and opposite force on the current-carrying conductor.
2. Activity 12.7: Demonstrating Force on a Conductor:
   • Materials: A small aluminum rod (approximately 5 cm), connecting wires, a strong horse-shoe magnet, a battery, a key, and a rheostat.
   • Procedure:
     • Suspend the aluminum rod horizontally using connecting wires.
     • Position the horse-shoe magnet so that the rod is located between its poles, with the magnetic field directed upwards (north pole below, south pole above).
     • Connect the rod in series with the battery, key, and rheostat, allowing current to flow from end B to end A.
   • Observation: The rod moves towards the left.
   • Reversal of Current: When the current direction is reversed, the rod moves towards the right.
3. Explanation of Displacement:
   • The displacement of the rod indicates that a force acts on it when placed in a magnetic field. The direction of this force reverses with the reversal of the current's direction.
   • If the magnetic field direction is changed to vertically downwards (by switching the poles of the magnet), the direction of force on the rod also reverses.
   • The force on the conductor is maximized when the current direction is perpendicular to the magnetic field direction.
4. Fleming's Left-Hand Rule:
   • Definition: A simple rule to determine the direction of force on a current-carrying conductor in a magnetic field.
   • Application:
     • 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.
     • The second finger points in the direction of the current.
     • The thumb will then point in the direction of motion or the force acting on the conductor.
5. Applications of the Concept:
   • Devices that utilize the interaction between current-carrying conductors and magnetic fields include:
     • Electric motors
     • Electric generators
     • Loudspeakers
     • Microphones
     • Measuring instruments

12.4 - Domestic Electric Circuits

1. Main Supply of Electric Power:
   • In homes, electric power is supplied through a main supply (or mains), which can be delivered via overhead poles or underground cables.
2. Wiring System:
   • Live Wire: Usually insulated with red, this wire carries the positive voltage.
   • Neutral Wire: Typically insulated with black, this wire serves as the negative return path.
   • The potential difference between the live and neutral wires is 220 V in our country.
3. Electricity Meter and Main Fuse:
   • At the meter board, live and neutral wires enter through an electricity meter, passing through a main fuse to ensure safety.
4. Circuit Ratings:
   • Houses generally have two separate circuits:
     • 15 A Circuit: Used for high-power appliances such as geysers and air coolers.
     • 5 A Circuit: Used for lower power devices like bulbs and fans.
5. Earth Wire:
   • The earth wire, insulated in green, connects to a metal plate buried deep in the ground.
   • This wire serves as a safety measure for appliances with metallic bodies (e.g., electric presses, toasters).
   • It provides a low-resistance path for any leakage current, keeping the metallic body at earth potential, which reduces the risk of electric shock.
6. Schematic Diagram:
   • A typical domestic circuit diagram illustrates how appliances are connected across live and neutral wires. Each appliance has its own switch to control current flow.
   • Appliances are connected in parallel to ensure each receives equal potential difference.
7. Electric Fuse:
   • An electric fuse is crucial in all domestic circuits. It protects appliances and wiring from damage due to overloading.
   • Overloading: This can occur if the live and neutral wires touch directly (due to damaged insulation) or if too many appliances are connected to a single socket.
   • During an overload, current surges occur, which can lead to short-circuiting, causing potential hazards.
   • The fuse works on the principle of Joule heating, melting when the current exceeds safe levels, thus breaking the circuit and preventing damage.
8. Conclusion:
   • Understanding domestic electric circuits is essential for safety and proper functioning. Awareness of the roles of live, neutral, and earth wires, as well as the function of fuses, helps mitigate risks associated with electrical use in households.

NCERT Science Notes - Class 10 | Science | Chapter - 12 | Magnetic Effects of Electric Current

NCERT Science Notes - Class 9 | Chapter 12 - Improvement in Food Resources