Class 10 Science Chapter 12 Magnetic Effects of Electric Current NCERT Solutions 2026 PDF Download

Ans: The compass needle is essentially a small bar magnet. When brought near another magnet, the magnetic field lines of the bar magnet interact with the magnetic field of the compass needle, causing it to experience a force and deflect.

Ans: Properties:
1. They originate from the North pole and end at the South pole (outside the magnet).
2. Inside the magnet, they move from South to North.
3. They form continuous closed curves.
4. The closer the lines, the stronger the magnetic field.
5. No two field lines ever cross each other.

Ans: If two field lines were to intersect, it would mean that at the point of intersection, the compass needle would point in two different directions simultaneously, which is impossible. Hence, they never cross.

Ans: Using the Right-Hand Thumb Rule:
- Inside the loop: The magnetic field lines go into the table (Downwards).
- Outside the loop: The magnetic field lines come out of the table (Upwards).

Ans: Stretch the thumb, forefinger, and middle finger of the left hand such that they are mutually perpendicular.
- Forefinger: Points in the direction of the Magnetic Field.
- Middle Finger: Points in the direction of the Current.
- Thumb: Points in the direction of the Force (Motion) exerted on the conductor.

[Image of Fleming's Left Hand Rule]

Ans: The earth wire (green insulation) provides a low-resistance conducting path for the current. It is connected to the metallic body of appliances (like iron, toaster). If there is any leakage of current to the metallic body, it flows directly to the earth, preventing the user from getting a severe electric shock.

Ans: The force is largest (maximum) when the direction of the current is perpendicular ($90^\circ$) to the direction of the magnetic field.

Ans: A fuse is a safety device made of a wire with a low melting point (e.g., alloy of lead and tin). It is connected in series with the live wire. If the current exceeds a safe limit (due to short-circuit or overload), the fuse wire gets heated, melts, and breaks the circuit, stopping the current flow and protecting appliances.

Ans: 1. Electric Fuse: Prevents damage from excessive current.
2. Earthing: Prevents electric shocks from metallic appliances.

Ans: Look at the face of the coil:
- If current flows Clockwise, it acts as a South Pole.
- If current flows Anti-clockwise, it acts as a North Pole.

Ans: Inside a solenoid, the magnetic field lines are parallel straight lines. This indicates that the magnetic field is uniform at all points inside the solenoid.

Ans:

• Overloading: Connecting too many high-power appliances to a single socket, drawing excessive current.
• Short-Circuiting: When Live wire and Neutral wire come in direct contact (due to damaged insulation), reducing resistance to near zero and causing a huge current flow.

Ans: 1. Increasing the number of turns in the coil.
2. Increasing the current flowing through the coil.
3. Using Soft Iron as the core material.

Ans:

• AC: Direction of current reverses periodically. Frequency in India is 50 Hz. (Source: Power plants).
• DC: Current flows in a single direction. (Source: Battery).

Preference: AC is preferred because it can be transmitted over long distances with minimal loss of energy using transformers (stepping up/down voltage).

Ans: Imagine holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of the current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field.
It determines the direction of the magnetic field produced by a straight current-carrying conductor.

[Image of Right Hand Thumb Rule]

Ans:
1. Live Wire: Red (Old convention) or Brown (New convention). Carries current at 220V.
2. Neutral Wire: Black (Old) or Blue (New). At 0V potential.
3. Earth Wire: Green (Old) or Green/Yellow (New). Safety wire.

Ans: Using Fleming's Left-Hand Rule:
- Current (I) is towards West (direction of positive charge motion).
- Force (F/Deflection) is towards North.
- Point forefinger (Field) direction... It points Upwards.
Therefore, the direction of the magnetic field is Upward.

Ans: Soft Iron gains magnetism easily when current flows and loses it immediately when current stops (Temporary Magnet). Steel, however, retains magnetism even after the current stops (Permanent Magnet). For an electromagnet (like in electric bells or cranes), we need the magnetism to be controllable, so Soft Iron is used.

Ans: The frequency is 50 Hz.
Time period ($T$) = $1/50 = 0.02$ seconds.
It changes direction every half cycle, i.e., every $0.02/2 = 0.01$ seconds.

Ans: 220 Volts.

Ans: The direction of current is opposite to the motion of electrons. Use Fleming's Left-Hand Rule with the middle finger opposite to the electron's velocity.

Ans: The field lines near the wire are concentric circles. As we move towards the center of the loop, the circles become larger and larger. At the exact center, the field lines appear as straight lines perpendicular to the plane of the coil.

Ans: Fleming's Left-Hand Rule.