Magnetism

Which of the following objects can be strongly attracted by a magnet?

Two like poles of magnets brought close together will ...

Every magnet has two poles, namely ...

A bar magnet hung freely and able to rotate will always point toward ...

Which of the following materials cannot be attracted by a magnet?

The part of a magnet with the strongest attractive force is ...

Look at these methods! (1) Increase the number of turns. (2) Increase the electric current. (3) Replace the iron core with plastic. (4) Reduce the number of turns. The ways to strengthen an electromagnet's magnetic field are shown by numbers ...

The advantage of an electromagnet over a permanent magnet is ...

Oersted's experiment showed that ...

The appearance of electric current in a coil due to a changing magnetic field around it is called ...

A device that changes motion energy into electrical energy is ...

The main function of a step-up transformer is ...

The group of materials that are ferromagnetic (strongly attracted by a magnet) is ...

A way that can remove the magnetism of a magnet is ...

An ideal transformer has 200 turns in the primary coil and 1,000 turns in the secondary coil. If the primary voltage is 220 V, the secondary voltage is ...

The magnetic poles of an electromagnet can be reversed by ...

A coil is connected to a galvanometer. The needle deflects when a magnet is moved in and out of the coil, but not when the magnet is still inside the coil. The correct conclusion is ...

An ideal transformer steps the voltage down from 220 V to 55 V. If the current in the secondary coil is 4 A, the current in the primary coil is ...

The application of electromagnets in daily life is shown by ...

In an electric bell, pressing the button makes current flow so the iron core becomes a magnet and pulls the hammer. When the hammer moves, the contact breaks, the current stops, and a spring returns the hammer. This shows that ...