Difference of terms help.

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paulmdrdo

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please help. what does it mean when they say "voltage across" some component. and how is "voltage aross" different from "voltage drop"? I'm confused please help!
 

From a common reference:

Volt (or Volts): Unit of measure for electromotive force (EMF), the electrical potential between two points. An electrical potential of 1 volt will push 1 ampere of current through a 1-ohm resistive load.

So, voltage is always the difference in potential between two points. "Voltage drop" has the added implication of current flow (https://en.wikipedia.org/wiki/Voltage_drop). Thus, one may use the term "voltage drop" when referring to the voltage across a resistor versus simply "voltage across" a capacitor or insulator. However, it is not incorrect to refer to the voltage "across" a resistor.

Why is the distinction important to you?

John
 
it's because I cant answer this problem.



isn't that the voltage across a diode is always 0.7v? but I don't know how to determine if the diode here is forward bias or reverse.
 

That's no problem of terms, it's about understanding electrical circuits.

The diode voltage won't be "always 0.7 V", it's only in forward bias, in other words when the circuit is driving a current through the diode.

The solution is using two steps.
1. Calulate the voltages without a diode.
2. Decision. If the diode voltage is > 0.7, you have forward bias, recalculate the voltages and currents. If it's < 0.7 no diode current, use the solution from step 1.
 

what do you mean by calculate the voltages? the sources are given? please bear with me. :?:
 

In forward bias, the diode has to be replaced by 0.7 V voltage source. You are right, the voltages are all determined, you need to calculate the currents.
 

how would I calculate the current? what method should I use?
 

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