Concept of Magnetic Field
Oersted’s Experiments
With the help of these experiments, Oersted demonstrated the relationship between electricity and magnetism. The experiments provided direct evidence of the connection between electricity and magnetism.
Experiment Setup:
- A conducting wire connected to a battery to create an electric current.
- A compass needle placed near the wire.
Key Observations:
- When the electric current flowed through the wire, the compass needle deflected.
- noticeable when the current is large and the needle sufficiently close to the wire so that the earth’s magnetic field may be ignored.
- alignment of the needle is tangential to an imaginary circle which has the straight wire as its Centre and has its plane perpendicular to the wire
- The deflection increases on increasing the current or bringing the needle closer to the wire.
- Reversing the direction of the current reverses the orientation of the needle
Conclusions:
- moving charges produce magnetic fields in the surrounding space.
- The direction of the magnetic field follows the right-hand rule. It states that if the thumb points in the direction of the current, the fingers curl in the direction of the magnetic field.
Definition:
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. Denoted by \(\vec B\).
Magnetic Field Lines:
- Imaginary lines used to represent the magnetic field.
- Direction of field lines indicates the direction of the magnetic force.
- Lines emanate from the north pole and enter the south pole of a magnet.
Sources of Magnetic Fields:
- Permanent Magnets
- Electric Currents
- Earth’s Magnetic Field
Magnetic Force:
- A force that a magnetic field exerts on a moving charge or another magnetic material.
Units and Measurement:
- SI unit of magnetic field strength \(B\) is Tesla \(T\).
- Other unit – Gauss \(G\), where \(1 \, T = 10,000 \, G\).
