Polarised capacitors

These generally have larger capacitance values. Polarised capacitors have a positive pole and a negative pole, so they must be connected to a circuit the correct way round.

Mounting of polarised capacitors

Polarised capacitors may be either axially mounted (on their side, connected at each end) or radially mounted (upright with both connections at the bottom).

Non-polarised capacitors

These are usually much smaller than the polarised type, and have smaller capacitance values. These might range from a few picofarads to a few microfarads. They don't have positive or negative poles so they can be connected to a circuit either way round.

Applications of capacitors

Capacitors are used to smooth rectified alternating-current voltages into steady direct-current voltages. They can also be used to filter out fluctuations in a signal.

Capacitors are often used in series with resistors to achieve a time delay. The time it takes for the capacitor to become charged is related to the size of the capacitor and the value of the regulating resistor.

Diodes

A diode is a discrete component that allows current to flow in one direction only. It is a polarised component with two leads, called the cathode and the anode. The cathode is normally marked with a silver or coloured band or the symbol ' - '.

If the anode is connected to a higher voltage than the cathode, current will flow from anode to cathode. This is called forward bias.

If the diode is put in the circuit back to front, so that the voltage at the cathode is higher than the voltage at the anode, the diode will not conduct electricity. This is called reverse bias.

Using diodes to prevent damage to circuits

Diodes are normally used to prevent damage to other polarised components in circuits: eg a diode can protect against current flowing the wrong way if the battery is put in back to front.

Diagram of forward/reverse bias

Дата добавления: 2015-10-26