Magnetic Effects of Electric Current class 10 Notes

 

Magnetic Effects of Electric Current class 10 Notes

Introduction: 

        Electricity and magnetism are closely connected phenomena. When an electric current flows through a conductor, it produces a magnetic field around it. This important phenomenon is known as the Magnetic Effects of Electric Current. The discovery of this effect by Hans Christian Oersted showed that electricity can produce magnetism, laying the foundation of modern electromagnetism.

Magnetic Field and Magnetic Field Lines:

1. Magnetic Field:

• A magnetic field is the region around a magnet or a current-carrying conductor in which its magnetic force can be felt.
• If a small magnetic compass is placed in this region, its needle gets deflected, showing the presence of a magnetic field.

Examples:

• Around a bar magnet

• Around a straight current-carrying wire

• Around a current-carrying coil or solenoid

SI Unit of Magnetic Field: Tesla (T)
Measuring instrument: Magnetometer

2. Magnetic Field Lines:

• Magnetic field lines are imaginary lines used to represent the direction and strength of a magnetic field.
• They help us to visualize magnetic fields, which cannot be seen directly.

Properties of Magnetic Field Lines

1. Closed continuous curves:
   Magnetic field lines form closed loops.

   • Outside the magnet: from North pole to South pole

   • Inside the magnet: from South pole to North pole

2. Direction of field:
   The direction of the magnetic field at any point is given by the tangent to the field line at that point.

3. No two field lines intersect:
   If they intersected, it would mean two directions of magnetic field at one point, which is impossible.

4. Closeness shows strength:

   • Field lines closer together → Strong magnetic field

   • Field lines farther apart → Weak magnetic field

5. Maximum density near poles:
   Magnetic field is strongest at the poles of a magnet.

Magnetic Field Around a Bar Magnet

• Field lines emerge from the North pole and enter the South pole.

• Inside the magnet, field lines go from South to North, completing a closed loop.

• The field is strongest near the poles.

Diagram :- Magnetic Field Around Bar Magnet

Magnetic Field Due to a Current-Carrying Conductor

• When an electric current flows through a conductor, it produces a magnetic field around it. This phenomenon is called the magnetic field due to a current-carrying conductor.
• This was first discovered by Hans Christian Oersted in 1820, proving the relationship between electricity and magnetism.

Oersted’s Experiment:

Aim: To show that electric current produces a magnetic field.

Observation:

• A compass needle placed near a current-carrying wire gets deflected.

• When the direction of current is reversed, the compass deflects in the opposite direction.

Conclusion:

• Electric current produces a magnetic field around the conductor.

Magnetic Field Due to a Current Through a Straight Conductor

• When an electric current flows through a straight conductor, it produces a magnetic field around it. This shows the close relationship between electricity and magnetism and is an important concept in the chapter Magnetic Effects of Electric Current.

                        This effect was first demonstrated by Oersted’s experiment.

Magnetic Field Pattern Around a Straight Conductor

• The magnetic field lines around a straight current-carrying conductor are concentric circles.

• These circles lie in a plane perpendicular to the conductor.

• The center of these circles is the conductor itself.

The direction of magnetic field lines depends on the direction of current in the conductor.

Right-Hand Thumb Rule (Maxwell’s Right-Hand Thumb Rule)

This rule is used to find the direction of the magnetic field around a straight current-carrying conductor.

Statement:

• Hold the conductor in your right hand.

• The thumb points in the direction of current.

• The curled fingers show the direction of magnetic field lines around the conductor.

✔ This rule is very important for board exams.

Strength of Magnetic Field

The strength of the magnetic field around a straight conductor depends on:

1. Magnitude of current

   • More current → Stronger magnetic field

2. Distance from the conductor

   • Magnetic field is strongest near the conductor

   • Field strength decreases with distance

3. Nature of the surrounding medium

• Magnetic field is stronger in magnetic materials like iron

Effect of Direction of Current

• If the direction of current is reversed, the direction of the magnetic field also reverses.

• This can be observed using a compass needle placed near the conductor.

Magnetic Field Due to a Current Through a Circular Loop

• When an electric current flows through a circular conducting loop, it produces a magnetic field around it. The magnetic field pattern of a circular loop is more complex than that of a straight conductor and shows properties similar to a bar magnet.

Magnetic Field Pattern of a Circular Current-Carrying Loop

• Each small part of the circular loop behaves like a straight current-carrying conductor.

• The magnetic field lines around the loop combine to form a strong magnetic field at the centre.

• Near the wire, field lines are circular, while near the centre they become almost straight and parallel, indicating a uniform magnetic field.

The direction of the magnetic field depends on the direction of current.

Direction of Magnetic Field (Right-Hand Thumb Rule)

• To find the direction of the magnetic field at the centre of the loop:

Rule:

• Curl the fingers of your right hand in the direction of current in the loop.

• The thumb points in the direction of the magnetic field at the centre of the loop.

✔ Very important for Class 10 board exams

Factors Affecting Magnetic Field Strength

The strength of the magnetic field produced by a circular loop depends on:

1. Current through the loop

   • More current → Stronger magnetic field

2. Radius of the loop

   • Smaller radius → Stronger magnetic field at the centre

3. Number of turns in the loop

• More turns → Stronger magnetic field

Effect of Reversing Current

• When the direction of current in the loop is reversed, the direction of the magnetic field also reverses.

• This can be observed using a compass needle placed at the centre of the loop.

Magnetic Field Due to a Current in a Solenoid

• A solenoid is a long coil of insulated copper wire wound in the shape of a helix. When an electric current flows through a solenoid, it produces a strong and uniform magnetic field inside it. A current-carrying solenoid behaves like a bar magnet.

Magnetic Field Pattern of a Solenoid

• Inside the solenoid, magnetic field lines are:

  • Straight

  • Parallel

  • Equally spaced
    👉 This shows a uniform magnetic field.

• Outside the solenoid:

  • Magnetic field is very weak

  • Field lines are curved and spread out.

The magnetic field pattern of a solenoid is similar to that of a bar magnet.

Polarity of a Solenoid (Finding North and South Poles)

• The ends of a solenoid behave like magnetic poles.

Right-Hand Grip Rule:

• Hold the solenoid in your right hand.

• Fingers curl in the direction of current.

• The thumb points towards the North pole of the solenoid.

Strength of Magnetic Field in a Solenoid

The strength of the magnetic field produced by a solenoid depends on:

1. Current through the solenoid

   • More current → Stronger magnetic field

2. Number of turns per unit length

   • More turns → Stronger magnetic field

3. Nature of the core material

• Inserting a soft iron core greatly increases the field strength

Solenoid as an Electromagnet

When a soft iron core is placed inside a current-carrying solenoid, it becomes an electromagnet.

Properties of an electromagnet:

• Temporary magnet

• Magnetic strength can be increased or decreased

• Can be switched ON or OFF

Difference between magnetic field of Bar magnet and Solenoid

Bar Magnet	Solenoid
Permanent Magnet	Temporary Magnet
Fixed Strength	Adjustable Strength
Poles can not be changed	Poles can be reversed by reversing current

Applications of Solenoid

• Electric bell

• Electric relay

• Magnetic cranes

• Electric motors

• Loudspeakers

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. This force is due to the interaction between the magnetic field produced by the conductor and the external magnetic field. This principle is the basic working principle of an electric motor.

Experiment to Demonstrate the Force

Setup:

• A straight conductor is placed between the poles of a strong magnet.

• The conductor is connected to a battery and key.

Observation:

• When current flows through the conductor, it gets deflected.

• When the direction of current is reversed, the conductor moves in the opposite direction.

• When the magnetic field direction is reversed, the direction of force also reverses.

Conclusion:
A current-carrying conductor placed in a magnetic field experiences a force.

Fleming’s Left-Hand Rule

This rule is used to find the direction of force acting on the conductor.

Statement:
Stretch the thumb, forefinger, and middle finger of the left hand such that they are mutually perpendicular:

• Forefinger → Direction of magnetic field

• Middle finger → Direction of current

• Thumb → Direction of force (motion of conductor)

✔ Very important for board exams

Factors Affecting the Force on the Conductor

The force acting on a current-carrying conductor depends on:

1. Strength of magnetic field

   • Stronger field → Greater force

2. Magnitude of current

   • More current → More force

3. Length of conductor in the field

   • Greater length → More force

4. Angle between current and magnetic field

• Force is maximum when conductor is perpendicular to the magnetic field

• Force is zero when conductor is parallel to the magnetic field

Mathematical Expression (For Understanding)

$$F \propto BIL$$

Where:

• $\mathrm{F\; =\; force\; on\; the\; conductor}$

• $\mathrm{B\; =\; magnetic\; field\; strength}$

• $\mathrm{I\; =\; current\; through\; conductor}$

• $\mathrm{L\; =\; length\; of\; conductor\; in\; magnetic\; field}$

(Note:-Formula knowledge is sufficient at Class 10 level)

Special Cases

• If the conductor is parallel to the magnetic field → No force

• If the conductor is perpendicular to the magnetic field → Maximum force

Applications

• Electric motor

• Loudspeakers

• Moving-coil galvanometer

• Electric generators

AC current and DC current:

Key Points :

• AC is used for homes because it is easy to transmit over long distances.

• DC is used for devices that need a steady and constant voltage.

• AC can be converted to DC using rectifiers, and DC can be converted to AC using inverters.

Difference between AC and DC:

Feature	AC	DC
Full Form	Alternating Current	Direct Current
Direction of Flow	Changes periodically (reverses direction)	Flows in one direction only
Source	Generators (like power plants), mains supply	Batteries, cells, solar panels
Waveform	Sinusoidal, triangular, or square wave	Constant (straight line)
Frequency	50 Hz in India (changes direction 50 times/sec)	0 Hz (steady, no reversal)
Transmission	Can be easily transmitted over long distances	Not suitable for long-distance transmission
Applications	Domestic supply, motors, transformers	Electronic devices, battery-operated appliances, charging
Symbol	~	⎓ or –––––
Voltage	Varies with time	Constant

Domestic Electric Circuits 

• A domestic electric circuit is the arrangement of wires and electrical components used in homes to provide electricity safely and efficiently to electrical appliances. These circuits are designed to ensure proper voltage, prevent accidents, and allow control of electricity in different areas of the house.

Main Components of Domestic Electric Circuits

1. Electric Wires (Conductors)

   • Copper is commonly used because of high conductivity and ductility.

   • Wires are insulated with PVC to prevent electric shocks.

   • Types of wires:

     • Live wire (Red/Brown): Carries current to the appliance.

     • Neutral wire (Black/Blue): Completes the circuit back to the supply.

     • Earth wire (Green/Yellow): Provides safety by diverting current to the ground.

2. Switches

• Used to control the flow of current.

• Can be:

• Single-pole switch: Controls one appliance.

• Two-way switch: Allows controlling a light from two locations.

3. Fuses / MCB (Miniature Circuit Breaker)

   • Protect appliances from overcurrent.

   • Fuse: Melts if current exceeds safe limit.

   • MCB: Automatically cuts off current during overload or short circuit and can be reset.

4. Electric Meter

   • Measures the consumption of electrical energy in units (kWh).

5. Plug & Socket

   • Plugs are connected to appliances; sockets are connected to supply.

   • Ensure proper connection for safety.

6. Earthing (Grounding)

• Provides a safe path for excess current.

• Prevents electric shocks and appliance damage.

Types of Domestic Circuits

1. Series Circuit

   • Components connected one after another.

   • Same current flows through all components.

   • Rarely used in homes because:

     • If one appliance fails, all stop working.

     • Voltage across each appliance is divided.

2. Parallel Circuit (Most commonly used in homes)

• Appliances are connected in parallel across the supply.

• Each appliance gets full voltage.

• If one appliance fails, others continue working.

• Current through each appliance is independent.

Safety Measures in Domestic Circuits

1. Earthing: Prevents electric shocks.

2. Fuses/MCBs: Prevent overcurrent hazards.

3. Insulated wires: Avoid accidental contact.

4. Avoid overloading: Don’t connect too many devices to a single socket.

5. Use of residual current devices (RCCB): Protects from leakage currents.

Important Points to Remember (Exam point of view)

• Domestic circuits usually work on 230 V, 50 Hz AC supply.

• Parallel connection is preferred to ensure uniform voltage and independent operation.

• Live, neutral, and earth wires must be correctly identified and connected.

• Regular maintenance is necessary to prevent accidents.

Download : Magnetic Effects of Electric Current class 10 Notes

Download also : Important Questions on Magnetic Effects of Electric Current class 10

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