Posts Tagged ‘electronics’

A question for you from electronics !

Which of the following two circuits will give rectified output for the both the half cycles of a.c. input?

Law of mass action

When an intrinsic semiconductor is doped with pentavalent impurity, the number of free lectrons increases. Will it result in any change in the number of holes already present?

The answer is YES.

When the semiconductor is doped with pentavalent impurity, the n_e increases and will result in a decrease in n_h according to the relation.

n_i² = n_in_h

This relationship is called the mass action law.

When the no. of free electrons increases, greater no. of holes already present get neutralised.

The difference between electricity and electronics

Electricity is the branch of Physics (?) which deals with the flow of electrons and its effect. The electric bulb, electric iron etc are electric devices as they are based on the direct effects like heating effect of current.

Electronics is the branch of Physics (?) which deals with the control of the flow of electrons (by allowing or disallowing or regulating the percentage of flow) through a device.

The television, calculator, computer are all electronic devices. Evidently they are not limited to the direct effect of flow of electrons through a conductor or a resistor ar any other transducer.

Now, try to classify the following appliances into electric devices and electronic devices.

1. transistor radio
2. sodium vapour lamp
3. ups
4. television
5. electromagnet
6. geyser
7. calling bell
8. voting machine
9. soldering iron
10. quartz clock
11. desoldering machine
12. electric iron

Nowadays, many electric appliances are also fitted with some electronic component. Can you site some examples?

Doping

Doping is the deliberate addition of desirable impurities to an intrinsic semicounductor to modify its conducting propertires.

The impurity atoms added are called dopants and the semi conductor so formed is called extrinsic semiconductor.

Depending on the type of impurities added, extrinsic semiconduictors are divided into two : n -type and p-type.

Note:

The extrememly pure form of semiconductor is called intrinsic semiconductor.

The conductivity of an intrinsic semiconductor is extremely low (but greater than insulators), and therefore as such there is no much practical use of intrinsic semiconductor. But when suitably doped to make extrinsic semiconductor, it works wonders. We get greater control over the flow of electrons.