The text is about magnetic fields and coils. Identify the key concepts and their descriptions based on the provided text.

Key Concepts and Descriptions:

• Magnetic Field Lines: These are imaginary lines that represent the direction and strength of a magnetic field. They are formed by magnetic filings around a magnet.
• Coils (Катушки): When current flows through a coil of wire, it generates a magnetic field, similar to that of a bar magnet.
• Magnetic Field of a Coil: The magnetic field lines around a coil with current are closed loops, resembling those of a permanent magnet. They are directed from the north pole to the south pole outside the coil.
• Poles of a Coil: A coil with current has two poles: a north pole and a south pole, similar to a bar magnet.
• Interaction of Coils: Two coils with current can interact with each other due to their magnetic fields.
• Right-Hand Rule (for coils): To determine the direction of the magnetic field lines, if you grip the coil with your right hand such that your fingers point in the direction of the current, your thumb will point towards the north pole.
• Solenoid: A solenoid is a type of coil where the magnetic field inside is uniform and strong.
• Electromagnetism: The relationship between electricity and magnetism, as demonstrated by the magnetic field produced by a current-carrying coil.