The magnetic effect of current was discovered by Oersted in 1890. Oersted found that a wire carrying a current was able to deflect a compass needle.
It was concluded that a current flowing in a wire always gives rise to a magnetic field around it.
Demonstrate the magnetic effect of current:
1. When the direction of the current is North to the South, the North pole of the magnetic needle gets deflected towards the east.
2. When the direction of the current is reversed, so that it flows from the South to North, the North pole of the magnetic needle gets deflected towards the west.
Magnetic field patterns produced by current — carrying conductors having different shapes:
The patterns of magnetic field (or shape of magnetic field lines) produced by a current-carrying conductor depends on its shapes. We will now study the magnetic field patterns produced by:
- A straight conductor(0r straight wire) carrying current
- A circular loop(or circular wire) carrying current.
- A solenoid(long coil of wire) carrying current.
[1] Magnetic field pattern due to straight current- carrying- carrying conductor(straight current — carrying wire)
Note:-Maxwell's Right-hand thumb Rule is also known as Maxwell's corkscrew rule(corkscrew is a device for pulling corks from bottles and consists of a spiral metal rod and a handle)
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| Maxwell's corkscrew rule |
[2] Magnetic field pattern due to a circular loop(or circular wire) carrying current:
The magnitude of magnetic field produced by a current-carrying circular loop(or circular wire) at its centre is :-
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| Magnetic field due to circular loop |
- Directly proportional to the current passing through the circular loop (or circular wire).
- Inversely proportional to the radius of circular loop.
[3] Magnetic field due to solenoid:
The solenoid is long coil contains a large number of close turns of insulated copper wire.
The magnetic field produced by a current — carrying solenoid is similar to the magnetic field produced by a bar magnet.
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| Magnetic field due to solenoid |
- Magnetic field line insides the solenoid are in the farm of parallel straight lines. So it is a uniform magnetic field.
- Earth's magnetic field at a given place is uniform
The strength of magnetic field produced by a current carrying solenoid depends on:
- The number of turns in the solenoids:-The Larger the number of turns in the solenoid, the greater will be the magnetism produced.
- The strength of current in the solenoid:-The Larger the current passed through the solenoid, the stronger will be the magnetic field produced.
- The nature of core material used in making solenoid:-The use of soft iron rod as core in a solenoid produces the strongest magnetism.