Moving-coil microphone

Physics Assignment Help Online

Moving-coil microphone The moving-coil microphone (Fig. 43.24) has a diaphragm with a light coil attached. The coil is situated in the strong magnetic field of a cylindrical pot magnet. Sound waves cause the diaphragm to vibrate, and as the coil moves back and forth in the magnetic field an alternating e.m.f. is induced in it. This is fed […]

Telephone communication

Physics Assignment Help Online

Telephone communication The action of a telephone receiver or ear-piece has already been described on page 425. The transmitter or microphone of a telephone instrument consists essentially of two polished carbon discs, placed a short distance apart, the space between being filled with small carbon granules (Fig. 43.21). One of the discs is fixed and the other connected to […]

The choke

Physics Assignment Help Online

The choke The current in a d.c. circuit is controlled by means of a rheostat, but as the above example shows, this method is very wasteful of energy. The current in an a.c. circuit can also be controlled by a rheostat, but for some purposes it is better to use a choke. This consists of a low resistance […]

Advantage of a.c. over d.c. power transmission

Physics Assignment Help Online

Advantage of a.c. over d.c. power transmission One of the main advantages of a.c. is that it can be easily and cheaply changed from one voltage to another by a transformer with very little loss of energy. For this reason, electric power generally is conveyed by a.c., as it can be trans formed to very high voltage and […]

Energy losses in a transformer

Physics Assignment Help Online

Energy losses in a transformer A transformer is designed so that as little energy as possible is wasted inside it thus ensuring that its efficiency is as high as possible. Important features are: (1) low-resistance copper coils so that internal energy (12R) losses in the windings are small; (2) laminated core to reduce eddy current losses; (3) […]

The transformer

Physics Assignment Help Online

The transformer If an alternating current is passed through the primary coil of Faraday’s iron ring (page 488) j an alternating magnetic flux will be set up through the iron and will induce an alternating e.m.f. in the secondary coil. The magnitude of this induced e.m.f. will depend on the e.m.f. applied to the primary and on the […]

Practical dynamos

Physics Assignment Help Online

Practical dynamos One of the disadvantages of the simple dynamo as described above is that its e.m.f. is reduced to zero every half rotation. In practice, this difficulty is overcome by having a number of coils wound in slots cut in an iron cylinder called the armature. Each coil has its own pair of segments in a […]

D.c. dynamo compared with an electric motor

Physics Assignment Help Online

D.c. dynamo compared with an electric motor Comparison of the d.c. dynamo described above with the electric motor on page 437 will show that the two machines are identical in construction. If a simple d.c. dynamo is connected to a battery it will run as a motor. Conversely, if a simple electric motor is made to rotate it […]

How to increase the a.m.f. obtained from a simple dynamo

Physics Assignment Help Online

How to increase the a.m.f. obtained from a simple dynamo Anything which increases the rate of cutting of magnetic flux in a dynamo will increase the electromotive force obtained from it. There are several ways in which this may be done: (1) by increasing the number of turns in the coil; (2) by winding the coil on […]