# Active and Passive Devices

Discussion in 'General Electronics Chat' started by Danielolawale, Oct 9, 2005.

1. ### Danielolawale Thread Starter New Member

Oct 9, 2005
1
0
I saw on this site that a passive device is one that is incapable of controlling current by an external power supply. I thought a resistor can then not be a passive instrument since a reistor can control current when a power supply is connected to it. Recall - Ohm's Law. I'll love you to explain better on this issue. Thanks

2. ### Sebi Well-Known Member

Sep 24, 2005
59
0
Resistor is a passive device. In the power supply work as SENSOR. (give a current-depending voltage) For the CONTROLING still need an active device.

3. ### viterbi New Member

Oct 13, 2005
3
0
Generally, a passive device is one that does not contribute free electrons to a given circuit. An active device does contribute electrons to a given circuit (we call this amplification). A resistor is a passive device since it does not contribute electrons to a circuit. In fact it "steals" electrons from the circuit and converts them into heat!

4. ### mentaaal Senior Member

Oct 17, 2005
451
0

surely no electrons can be lost in the circuit by the resistor. What is being lost is energy by the action of pushing electrons through the resistor. if electrons were to be lost you would cause the atoms in the conductor to be +ively charged and stop the circuit being a circuit as there would be no easily removable electrons to transfer energy

5. ### jidhishs New Member

Oct 21, 2005
3
0

Energy required for pushing the electrons through the resistor is VOLTAGE. But something is converted in to heat .....is it voltage. ???? or power...if power P=VI , current is converted in to heat. current is the flow of electrons....so electrons should be converted in to heat.....(so circuit stops) or is it voltage??? we know H=I(square)RT.
I=V/R. so whether voltage is converted in to heat......????

so i think the heat is produced due to the collision of both +ve and -ve ly charged particles.....for collision of electrons both voltage and current(flow of electrons due to voltage difference) is required...ie nothing but power....so power is converted in to heat.

6. ### thingmaker3 Retired Moderator

May 16, 2005
5,072
6
Energy is measured in Joules, not Volts. Electromotive Force is measured in Volts. Voltage is Energy Per Unit Charge. One Volt equals One Joule Per Coulomb of Charge.

"Heat" is defined as energy in transit from a higher temperature object or system to a lower temperature object or system. Heat is also measured in Joules.

Heat and Work are interchangeable. Work is also measured in Joules.

Power is the rate at which energy is expended or the rate at which work is done. Power is the rate at which heat is dissipated.

One Watt is equal to One Joule Per Second.
One Joule is equal to One Watt-Second.

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

7. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
Passive and active devices are characterised by their control on the circuit operation, typically the control of current flow.