# Why doesn't the voltage of the load fluctuate in a Zener Diode circuit?

I'm very new to this field so sorry for this silly question.

What I've learnt is that when any number of devices are connected in parallel (and none in series with the battery) with the battery, the potential difference across all the devices is equal to that of the battery.

If 2 resistors are connected in series in one 'line' of the parallel circuit, how the potential is spent by the two resistors, their values of resistances, etc. shouldn't affect the voltage of the other 'lines' of the parallel circuit.

So when the Zener diode and the load are connected in parallel with the voltage source, whether the voltage is constant in the diode or not shouldn't affect the load from having the same potential difference as the voltage source right?

And yet, even though parallelly connected with the load, the diode manages to affect the voltage of the load.

How is this accomplished?

P.S - I may have misused some terms so sorry in advance :)

• Can you try drawing a schematic of the circuit you are asking about? Exactly how your battery or voltage source, zener, and load are connected isn't clear from your wording so a diagram would help us better answer the question. You can use the built-in schematic drawing tool if you like. Nov 26 '19 at 16:33
• You already asked this question on physics.se. What was unsatisfactory about the answer you got there (and then, why did you accept an answer there), and what more are you asking us to explain on EE? Nov 26 '19 at 17:39
• Yes, I did ask it there but the answer given didn’t help me. I thought it did earlier and realised it didn’t afterwards. The answer given by Vincente Cuna cleared it for me by making me realise I had to take the resistance into consideration too while looking at the structure of the parallel circuit. Nov 26 '19 at 17:43

When using a Zener diode in parallel to regulate voltage, you do not connect the Zener directly to the voltage source. Instead, you connect it with a resistor (or other circuitry) capable of handling the voltage drop and current required. See this example circuit, where $$\V_z\$$ is the Zener voltage: simulate this circuit – Schematic created using CircuitLab

The voltage across $$\R_z\$$ will be $$\(Vcc-V_z)\$$, while the voltage across $$\R_{load}\$$ will be $$\V_z\$$. The power rating of $$\R_z\$$ should be at least $$\\frac{(Vcc-V_z)^2}{R_z}\$$

You are correct in the statement that connecting components in parallel to an (ideal) voltage source results in that same voltage across each parallel branch. But when connecting things in series with a voltage source before parallel branches, then this no longer applies.

• Thanks! Any documents/sites to read up on the last part of your answer? Nov 26 '19 at 16:49
• This is a relevant related question: electronics.stackexchange.com/questions/127525/… Nov 26 '19 at 16:52
• Thanks again for your help! Nov 26 '19 at 16:58