transistor cant understand even a bit

**vk6kro** · Nov16-09, 02:27 AM

i cant understand how a potentiometer can vary the electric field of the battery acting on the transistor.
but i know how potentiometer works i learnt from this site
http://www.allaboutcircuits.com/vol_1/chpt_6/1.html
i just cant digest how it is used in this transistor characteristics and what is its role and how can it vary the electric field of the battery acting the Emitter BAse

You understand how a potentiometer works but you don't understand how it produces a variable voltage?
Its only function is to produce a variable voltage, so you do not understand how it works.
That web site explains it very well.

As you increase the voltage across the base emitter junction of a transistor (or any other diode) in the forward direction, the current through the diode starts off at zero and stays there at zero until the diode starts to conduct at about 0.6 volts for a silicon diode and at different voltages for other types of diodes. Above 0.6 volts, the diode current will increase rapidly and be limited only by the available current.

You need a variable voltage to test the transistor and a potentiometer gives you a variable voltage. So, why is that a problem?

**sudar_dhoni** · Nov16-09, 03:55 AM

Originally Posted by vk6kro

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You understand how a potentiometer works but you don't understand how it produces a variable voltage?
Its only function is to produce a variable voltage, so you do not understand how it works.
That web site explains it very well.

As you increase the voltage across the base emitter junction of a transistor (or any other diode) in the forward direction, the current through the diode starts off at zero and stays there at zero until the diode starts to conduct at about 0.6 volts for a silicon diode and at different voltages for other types of diodes. Above 0.6 volts, the diode current will increase rapidly and be limited only by the available current.

You need a variable voltage to test the transistor and a potentiometer gives you a variable voltage. So, why is that a problem?

u didnt understand my question
i never told i didnt understand how potentiometer works
see what i have asked

"i cant understand how a potentiometer can vary the electric field of the battery acting on the transistor.
but i know how potentiometer works i learnt from this site
http://www.allaboutcircuits.com/vol_1/chpt_6/1.html
i just cant digest how it is used in this transistor characteristics and what is its role and how can it vary the electric field of the battery acting the Emitter BAse"

potentiometer is just an instrument used to vary the voltage drops
if u send 10V by adjusting the slider u can drop 4V and send only 6V to the appliance
this is possible if current flows through it
in the case of transistor battery only establishes electric field within the transistor
how can potentiometer vary the electric field which is acting on the transistor?????????

**vk6kro** · Nov16-09, 04:32 AM

There is a current flowing in the potentiometer, so the voltage that comes out of the slider is just as real as the voltage that comes out of the battery.

Transistor currents 4.PNG

In the above circuit, the voltmeter doesn't draw any current. What does it read when the slider is in the centre position on the potentiometer?

If you put a transistor across the voltmeter, why would it not get the same voltage on it as the voltmeter?

**sudar_dhoni** · Nov16-09, 05:44 AM

Originally Posted by vk6kro

There is a current flowing in the potentiometer, so the voltage that comes out of the slider is just as real as the voltage that comes out of the battery.

Attachment 21857

In the above circuit, the voltmeter doesn't draw any current. What does it read when the slider is in the centre position on the potentiometer?

If you put a transistor across the voltmeter, why would it not get the same voltage on it as the voltmeter?

the voltmeter will draw little current and measure 6V as the remaining 6 would have already dropped.What u r saying is applicable only if we draw current from the battery.
But in transistor the battery is just applying electric field and not drawing current.
How can the electric field be varied but using potentiometer
Mr vk6kro plz bear with me.If u feel that i am pestering u plz mention it
here after i wont trouble u

**vk6kro** · Nov16-09, 09:43 AM

You can put a voltage across anything. Of course. Why couldn't you? If it is already variable it will still be variable.

It will draw current if it is a conductor or it will not draw current if it is an insulator.

Why do you keep insisting that a transistor will not draw current?
It will draw a current as soon as the minimum voltage is reached for the base emitter junction to start conducting. This is only a very small voltage. For higher voltages, it will draw a current.

What country are you in?

**sudar_dhoni** · Nov16-09, 10:03 AM

Originally Posted by vk6kro

You can put a voltage across anything. Of course. Why couldn't you? If it is already variable it will still be variable.

It will draw current if it is a conductor or it will not draw current if it is an insulator.

Why do you keep insisting that a transistor will not draw current?
It will draw a current as soon as the minimum voltage is reached for the base emitter junction to start conducting. This is only a very small voltage. For higher voltages, it will draw a current.

What country are you in?

i am from INDIA
could u plz tell me then what is the function of battery in npn transistor
i thought that transistor will draw current from the battery only after the electrons in the n type have gone to the base to maintain the concentration of electrons in the n type
i.e the electrons from -terminal will flow to emitter
in that way transistor draws current
but this happens only after the electrons in the n type have gone to base due the influence of the electric field SET UP BY THE BATTERY WHICH HOW CAN U VARY ?

I WILL EXPLAIN MY QUESTION IN DETAIL
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