CBSE Class 10 Science – Chapter 13: Magnetic Effects Of Electric Current – Detailed Notes & Explanation

Magnet: Any object that attracts any other objects that are made from iron, nickel, cobalt is called magnet.

Uses Of Magnet:

• Magnets are used in magnetic compass, door bells, and refrigerators.
• Magnets are used in dynamos, motors, loudspeakers, microphones etc.
• Ceramic magnets are used in computers.
• Magnets are used in toys to give a magical effect.

Magnetic Field:

Magnetic field lines are imaginary lines, which depict the strength and direction of the magnetic field. It is a vector quantity. 

Properties Of Magnetic Field Lines:

• They form closed loops
• They never intersect with each other.
• The magnetic field lines are crowded near the pole where the field is strong and spread apart from each other where the field is weak.
• They flow from the South Pole to the north pole within a magnet and north pole to south pole outside.

Magnetic Field Lines Due To Current Carrying Conductor :

The Magnetic field lines around a straight conductor carrying current are concentric circles whose centers lie on the wire. The direction of magnetic field lines can be determined using the Right-Hand Thumb Rule.

Right Hand Thumb Rule: Thumb rules state that if the thumb of the right hand points along the direction of current, then the remaining curled fingers of the same hand give the direction of the magnetic field due to the current.

Magnetic Field Due To Current Carrying Coil:

A wire develops a ring-shaped magnetic field as current flows through it.

The magnetic compass needle may be deflected by this magnetic field.

The magnetic field has a stronger field strength:

   (a) Closer to the wire,

   (b) if the current is increased.

Magnetic Field Due To Current Carrying Solenoid:

A wire is wound up into a spiral shape to form a coil of wire, also known as a solenoid.

The magnetic field’s shape when an electric current is flowing is extremely reminiscent to a bar magnet’s field.

A solenoid has a powerful and consistent field inside.

A stronger overall magnetic field is created by the tiny magnetic fields produced by the current in all of the coils.

Force on current carrying conductor: A magnetic field is created by an electric current flowing through a conductor. A magnet positioned close to a conductor experiences a force from the field that was thus created. Additionally, the current-carrying conductor experiences an equal and opposite force from the magnet.

When the magnetic field (B) and the current carrying wire of length (L) are perpendicular, then force on the wire is given by: F=BIL

Flemings left hand rule: A force perpendicular to the field’s direction and the direction of the current flow is experienced by a current-carrying conductor when it is exposed to an external magnetic field. When a current-carrying conductor is placed in a magnetic field, the direction of the force acting on it can be determined using Fleming’s left-hand rule. 

Direct Current: The unidirectional flow of an electric charge is referred to as direct current. Current flows in one direction only. Direct current can flow through conductors like wires, but it can also flow through semiconductors and even a vacuum.

Alternating Current:

A current that alternates in size and polarity on a regular basis is known as an alternating current. In contrast to Direct Current, or DC, which constantly runs in a single direction, it can alternatively be described as an electrical current that frequently changes or reverses its direction.

Difference Between Ac And Dc Current:

The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically. Most power stations constructed these days produce AC. In India, the AC changes direction after every 1/100 second, that is, the frequency of AC is 50 Hz. An important advantage of AC over DC is that electric power can be transmitted over long distances without much loss of energy.

Difference Between Ac And Dc Current:

Domestic Circuit:

Either underground cables or overhead wires are used to supply electricity to a home. Three distinct insulated wires make up the cable:

(a) Live wire 

(b) Neutral wire 

(c) Earth wire

The earth wire often has a green insulation cover, whereas the live and neutral wires typically have red and black insulation covers respectively. According to the new International Convention, live wires have insulation covers that are brown, while neutral and earth wires have insulation covers that are light blue and green (or yellow), respectively. The live and neutral wires have a 220 V potential difference. At the neighborhood sub-station, the neutral and earth wires are connected so that their respective potentials are both zero.

• Fuse is the most important safety device, used for protecting the circuits due to short-circuiting or overloading of the circuits.
• Short-circuiting typically happens when a conductor connecting a circuit’s endpoints has an extremely low resistance compared to the rest of the circuit. When the live (positive) and neutral (negative) wires in a household connection come into direct touch with one another, short-circuiting happens.
  • Damage to the insulation of the power-lines
  • A fault in an electric appliance due to which current does not pass through it.
  • Overloading

What are Magnetic Effects of Electric Current?

Color Coding of wires in a cable :

Wire	Colour
	Old Convention	New Convention
Live (L)	Red	Brown
Neutral (N)	Black	Light Blue
Earth (E)	Green	Light Blue

• The colour coding of wires help us to connect the switch, fuse, socket etc. through proper wire in house wiring.
• The live wire is at a higher potential of 220V whereas the neutral wire is at the ground potential of 0V.
• Overloading is the process of over heating of a wire due to excess current drawn by all the appliances than the permitted limit for that wire.
• Short-circuiting is the process of over heating which may even cause fire when the live wire and the neutral wire come in contact due to defective or damaged wiring.
• An electric fuse is a safety device which is used to limit the current in an electric circuit. It safeguards the circuits and the appliances connected in that circuit from being damaged.
• An alloy of lead and tin is used as the material of the fuse wire because it has a low melting point (≅ 250°C) and its specific resistance is more than that of copper and aluminium.
• The thickness of a fuse wire depends on its current rating. Higher the current rating, thicker is the fuse wire.
• A fuse is always connected in series with the live wire before the appliance.
• The fuse provided with an electric appliance to protect it against electric faults must be of current rating slightly higher than the maximum current that can be drawn by the appliance before being over heated.
• A switch is an on-off device for current in a circuit. It is connected in the live wire.
• To avoid the risk of electric shocks, the metal body of an electrical appliance is earthed. It is necessary to remove paint from the body part where earth connection is to be made.
• In a three pin plug, the top pin is for earthing, the pin on the left is for live and the pin on the right is for neutral.
• In a three pin socket, the upper hole is for earth connection, while the hole on the right side is for connection to the live wire and the hole on the left side is for connection to the neutral wire.
• All electrical appliances such as bulbs, fans, sockets, etc. are connected in parallel across the live wire and the neutral wire.