Question about Current drawn and Voltage drop

[zeitcheist]

Meron lang po sana ako gusto i-confirm..

Alin po sa dalawa sa baba ang tama:

1. An element in a circuit draws a certain amount of current that it needs, therefore, only the voltage needs to be controlled.
2. An element in a circuit accepts any amount of current, therefore current across must be controlled.

Or pareho po dapat i-control? Pano po malalaman exactly how much ung voltage and current at a single point sa circuit, kapag may mga ICs and transistors and diodes na?

Hehe, senxa na po, tagal ko na tanong to eh, kahit foreign forums yang parehong yan sagot nila, salitan lang, so hindi ko talaga alam kung ano ang tama.. ^^

[rdpzycho]

depende 'yan sa load. kung purely resistive refer to Ohm's law.

example: 220V 100W heater, equivalent resistance ~480 ohms. adjust the voltage, magbabago ang current, consequently pati power.

sa active elements naman, refer to their equations. but mostly it works on some regulated voltage, pero siyempre pwede mo ring i-design to work on variable voltage.

don't be concerned too much with what you are going to control because different circuits need different approaches, pero karamihan ng circuit works on a certain voltage and they will draw their current from that.

current regulation mostly used naman sa battery charging, or torque control ng motor.

always remember, closely related ang voltage at current dahil 'yung voltage 'yung potential para makagawa ng current.

[zeitcheist]

depende 'yan sa load. kung purely resistive refer to Ohm's law.

example: 220V 100W heater, equivalent resistance ~480 ohms. adjust the voltage, magbabago ang current, consequently pati power.

sa active elements naman, refer to their equations. but mostly it works on some regulated voltage, pero siyempre pwede mo ring i-design to work on variable voltage.

don't be concerned too much with what you are going to control because different circuits need different approaches, pero karamihan ng circuit works on a certain voltage and they will draw their current from that.

current regulation mostly used naman sa battery charging, or torque control ng motor.

always remember, closely related ang voltage at current dahil 'yung voltage 'yung potential para makagawa ng current.

1. In reality, meron po ba talaga na purely resistive circuit? Wala po di ba? Tama or mali?
2. In theory po, Ohm's Law ang basic, since constant po ang resistance ng isang element, does it follow na kung mababa ang voltage requirement ng element eh mataas ang current na kino-consume nito? Parang hindi.. So mali ung nasa isip ko.. Kasi 'til now hindi ko pa rin alam  kung ano appropriate na resistance ang need sa isang part ng isang circuit.. I mean the computation behind.. ^^

[rdpzycho]

1. yup walang purely resistive circuit, pero at low frequencies almost negligible ang parasitics ng resistor tulad ng sa heater, so you basically apply Ohm's Law.

2. what do you exactly mean by an element? low voltage doesn't necessarily mean high current and vice versa, depende lahat 'yan sa requirements ng circuit. example an LED only needs around 5mA to 20mA at low voltage. pero kung constant power ang pinag-uusapan, low voltage high current = high voltage low current, that is kung "constant power".

computation ng resistance is once against depende sa circuit. kapag may active elements na, 'di lang Ohm's Law ang kailangan mo, pati 'yung equations pertaining to the active element, most can be understood with Kirchoff's Laws. halimbawa sa simpleng Common Emitter transistor na may beta na 50 at kailangan mo ng 100mA sa output, 100mA / 50 = 2mA. [V(input to base) - V(be)] / 2mA = resistance needed for the required 2mA input to base.

[zeitcheist]

1. yup walang purely resistive circuit, pero at low frequencies almost negligible ang parasitics ng resistor tulad ng sa heater, so you basically apply Ohm's Law.

2. what do you exactly mean by an element? low voltage doesn't necessarily mean high current and vice versa, depende lahat 'yan sa requirements ng circuit. example an LED only needs around 5mA to 20mA at low voltage. pero kung constant power ang pinag-uusapan, low voltage high current = high voltage low current, that is kung "constant power".

computation ng resistance is once against depende sa circuit. kapag may active elements na, 'di lang Ohm's Law ang kailangan mo, pati 'yung equations pertaining to the active element, most can be understood with Kirchoff's Laws. halimbawa sa simpleng Common Emitter transistor na may beta na 50 at kailangan mo ng 100mA sa output, 100mA / 50 = 2mA. [V(input to base) - V(be)] / 2mA = resistance needed for the required 2mA input to base.

1. Ah okay po..
2. So need po talaga ung equations associated sa mga elements, pati different configurations.. Meron po kayo link for tutorial ng basic hardware design including ung computations ng resistances used?
Thanks po..

[rdpzycho]

marami niyan sa net, pero kung mas gusto mo sa libro, maraming nagre-recommend ng Art of Electronics.

[zeitcheist]

marami niyan sa net, pero kung mas gusto mo sa libro, maraming nagre-recommend ng Art of Electronics.

Thanks po! Hanap po ako.. Sino po author nito?

[rdpzycho]

Art of Electronics - Paul Horowitz, Winfield Hill.

[zeitcheist]

Art of Electronics - Paul Horowitz, Winfield Hill.

Salamat po ng marami! ^^

[ax30g]

Art of Electronics - Paul Horowitz, Winfield Hill.

Sir meron ba nito sa Pinas?

[roche_carrillo]

pare...mag aral ka sa basic circuit para makuha mo ang mga kailangan moh..sa ohm's law dapat mag aral ka.sa capacitor naman at sa inductor..bili kana lng nang libro sa electrical circuits or pocket books related sa electronics at electrical...sa akin ay ACER ang books na ginamit ko at ROXAS...sa cebu dami...sa inyo kaya nandyan sa national bookstore lng yan.

[dummy_c]

THE ART OF ELECTRONICS – 2nd edition:

http://rapidshare.com/files/419464262/TAOE_2E_warezholicari.com.rar.html

or
http://www.megaupload.com/?d=4Q2Q5Q0B

or
http://hotfile.com/dl/69827649/50ba6f5/TAOE_2E_warezholicari.com.rar.html

or
http://www.fileserve.com/file/E7bRDsE

 

[tony]

Sir meron ba nito sa Pinas?

sa Alexan, meron nyan, nasa 3500 ang hardbound book....