Electromagnetism

Direct Current Direct current is a uniform current flowing in one fixed direction in a circuit Direct current (d.c) is usually supplied by acid-based batteries or dry cells.  A common example of acid-based (electrolyte) batteries is the car battery.  The figure below shows the graph of current supplied by a dry cell over time. Alternating … Read more

A generator can be modified to an a.c generator by replacing its commutators with two (separate) slip rings. The two slip rings rotate in tandem with the armature.  Carbon brushes connect the armature to the external circuit. The armature is initially at the vertical position. No magnetic flux is cut and hence no induced current … Read more

The figure above shows the illustration of a simple direct current (d.c.) generator. You should notice that the simple d.c generator is almost the same as the d.c. motor except that the battery in the d.c. motor is removed and replaced by a resistor. The direct current generator produces electric current (or voltage) base on … Read more

When a bar magnet is inserted into a solenoid, the solenoid will cut the magnetic flux of the bar magnet. This will induce a current and emf in the solenoid. The induced current will produce another magnetic field around it. The pole of the magnetic field and direction of the induced current can be determined … Read more

When a straight conductor (or wire) moves and cut a magnetic field, emf will be induced across the conductor. If the conductor is in a complete circuit, the current will flow in the conductor. The direction of the current induced can be determined by using Fleming’s Right Hand Rule, as explained in the video below. … Read more

There are 2 principal laws of electromagnetic induction: Faraday’s law Lenz’s law Faraday’s Law The magnitude of the induced e.m.f is determined by Faraday’s Law. Faraday’s Law states that the magnitude of the induced e.m.f is directly proportional to the rate of change of magnetic flux through a coil or alternatively the rate of the … Read more

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