Electromagnetism

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

A solenoid is a long coil made up of a numbers of turns of wire. Magnetic Field Pattern Figure (a) illustrates the field pattern produced by a solenoid when current pass through it. The field lines in the solenoid are close to each other, indicates that the magnetic field is stronger inside the solenoid. We … Read more

Field Pattern Figure (a) below shows the field pattern produced by a current flowing in a circular coil. In SPM, you need to know the field pattern, the direction of the field and the factors affect the strength of the field. The direction of the field can be determined by the Right-Hand Grip Rule. Grip … Read more

Magnetic Field Pattern (Figure (a)) The magnetic field generated by a straight wire is concentric circles around the wire as shown in figure (a) above. Take notes that when the direction of the current is reversed, the direction of the magnetic field line is also reversed. The direction of the magnetic field line can be … Read more

When current passes through a conductor, the magnetic field will be generated around the conductor and the conductor becomes a magnet. This phenomenon is called electromagnetism.  Since the magnet is produced by electric current, hence it is called the electromagnet. An electromagnet is a type of magnet in which the magnetic field is produced by … Read more