Magnetism and Magnetic Effect of Current
NCERT Class 10 • Science • Chapter "Magnetic Effects of Electric Current" | NCERT Class 6 • Science • Chapter "Fun with Magnets"
Magnetism and Magnetic Effect of Current
A magnet attracts iron, nickel and cobalt and always has two poles that cannot be separated. The great discovery of this topic is that an electric current also produces a magnetic field, which means electricity and magnetism are two aspects of the same phenomenon.
Magnetic Field and Field Lines
- A magnetic field is the region around a magnet in which its force can be felt.
- Field lines run from the north pole to the south pole outside the magnet and from south to north inside it.
- Field lines never intersect, because two directions of the field at one point is impossible.
- Where field lines are crowded, the field is strong; where they are far apart, it is weak.
- A freely suspended magnet always rests in the north south direction, which is the principle of the compass.
- Like poles repel and unlike poles attract, and repulsion is the surer test of magnetism.
Magnetic Effect of Current
- Oersted observed that a compass needle placed near a current carrying wire is deflected, proving that current produces a magnetic field.
- Around a straight conductor the field lines are concentric circles whose direction is given by the right hand thumb rule.
- In that rule, the thumb points along the current and the curled fingers give the direction of the field.
- A solenoid is a long coil of wire; when current flows, it behaves like a bar magnet with a north and a south end.
- Placing a soft iron core inside a solenoid makes an electromagnet, which is strong and can be switched off.
- A current carrying conductor placed in a magnetic field experiences a force, whose direction is given by Fleming's left hand rule.
- This force is the working principle of the electric motor, which converts electrical energy into mechanical energy.
| Rule | Used For |
|---|---|
| Right hand thumb rule | Direction of field around a straight conductor |
| Fleming's left hand rule | Direction of force on a conductor in a field |
| Fleming's right hand rule | Direction of induced current in a generator |
Electromagnet — a solenoid with a soft iron core that acts as a strong magnet only while current flows through it.
Hindi me samjhein
दक्षिण हस्त अंगूठा नियम बताता है कि सीधे तार के चारों ओर क्षेत्र किस दिशा में है। फ्लेमिंग का वाम हस्त नियम बताता है कि क्षेत्र में रखे धारावाही चालक पर बल किस दिशा में लगेगा।
Exam me kaise aata hai
- Who discovered the magnetic effect of current — Oersted
- Field lines outside a magnet go from — north pole to south pole
- A solenoid with a soft iron core makes an — electromagnet
- Force on a conductor in a field is found by — Fleming's left hand rule
UPSC/State PSC ke liye
- Magnetic field lines never intersect, since an intersection would mean the compass needle points in two directions at the same point.
- Repulsion is the surer test of magnetism because an unmagnetised iron piece is also attracted by a magnet, but never repelled.
Yahan confuse hote hain
✗ Magnetic field lines can cross | Field lines never intersect | ✓
✗ Attraction is the surest test of magnetism | Repulsion is the surer test | ✓
✗ A single magnetic pole can exist alone | Poles always exist in pairs | ✓
Ek nazar me
- Field lines run north to south outside a magnet and never intersect.
- Oersted showed that current produces a magnetic field.
- Right hand thumb rule gives the field around a straight conductor.
- Fleming's left hand rule gives the force, which drives the electric motor.