Electromagnetism

When a magnet is moved into and out of the solenoid, magnetic flux is being cut by the coil.  The cutting of magnetic flux by the wire coil induces an e.m.f in the wire.  When the solenoid is connected to a closed circuit, the induced current will flow through the circuit. The production of electric … Read more

When 2 current-carrying conductors are placed close to each other, a force will be generated between them. If the current in both conductors flows in the same direction, they will attract each other, whereas if the current is in opposite direction, they will repel each other. This force is due to the interaction between the … Read more

Loud Speaker The loudspeaker contains a cylindrical coil which is free to move in a radial magnetic field set up by a strong cylindrical permanent magnet. The magnet has the central South Pole and the surrounding North Pole. The field lines are therefore radial and at right angles to the turns of the coil. When … Read more

An electric motor converts electrical energy to kinetic energy. The diagram above shows the structure of a simple direct current motor (DC motor). It consists of a rectangular coil of wire placed between 2 permanent magnets. The coil is soldered to a copper split ring known as a commutator. 2 carbon brushes are held against … Read more

Light Indicator A light indicator which has lower inertia is used to increase the sensitivity of the meter. Linear Scale Due to the radial magnetic field and the cylindrical soft-iron core, a linear scale is produced. A linear scale is more accurate and easier to be read. Mirror A mirror is used to prevent parallax … Read more

If a current-carrying coil is placed in a magnetic field (As shown in the diagram above), a pair of forces will be produced on the coil. This is due to the interaction of the magnetic field of the permanent magnet and the magnetic field of the current-carrying coil. The diagram below shows the catapult field … Read more

We have learned that when current flows in a conductor, a magnetic field will be generated. When the current-carrying conductor is placed in a magnetic field, the interaction between the two magnetic fields will produce a resultant field known as the catapult field as shown in the figure below. The catapult field is a non-uniform … Read more

An electromagnet is used in the earpiece of a telephone. The figure shows the simple structure of a telephone earpiece. When you speak to a friend through the telephone, your sound will be converted into electric current by the mouthpiece of the telephone. The current produced is a varying current and the frequency of the … Read more

A relay is an electrical switch that opens and closes under the control of another electrical circuit. The switch is operated by an electromagnet to open or close one or many sets of contacts. A relay has at least two circuits. One circuit can be used to control another circuit. The 1st circuit (input circuit) … Read more

When the switch is on, the circuit is completed and current flows. The electromagnet becomes magnetised and hence attracts the soft-iron armature and at the same time pull the hammer to strike the gong. This enables the hammer to strike the gong. As soon as the hammer moves towards the gong, the circuit is broken. … Read more