A 8 V Zener diode along with a series resistance R is connected across a 20 V supply (as shown in the figure). If the maximum Zener current is 25 mA, then the minimum value of R will be ____ Ω.
A 8 V Zener diode along with a series resistance R is connected across a 20 V supply (as shown in the figure). If the maximum Zener current is 25 mA, then the minimum value of R will be ____ Ω.
Correct Answer: 480
Approach Solution - 1
To find the minimum value of the series resistance R, we start by analyzing the circuit. The Zener diode maintains a constant voltage of 8 V across it when it is functioning in the breakdown region. Given the supply voltage is 20 V, the voltage across the series resistor R is:
VR = 20 V - 8 V = 12 V
The maximum Zener current, IZ, is 25 mA. Applying Ohm's law to the resistor:
IZ = VRR
Rearranging to find R:
R = VRIZ
Substituting the known values:
R = 12 \text{ V}{0.025 \text{ A}} = 480 \Omega
The minimum value of the series resistance R is confirmed to be 480 Ω, which fits within the expected range of 480 to 480 Ω.
Approach Solution -2
R will be minimum when RL is infinitely large, so
RZener=\(\frac{8}{25×10^{−3}}\)
RZener=320 Ω
So, \(\frac{R}{R_{Zener}}=\frac{12}{8}\)
R=\(\frac{12}{8}\)×320
R=480 Ω
So, the answer is 480 Ω.
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Concepts Used:
Electric Current
Defining Electric Current
It is the rate of flow of electrons in a conductor. SI Unit - Ampere (A).
Electrons are negatively charged particles hence when they move a number of charges moves.
Note:- The ability of a particular substance to conduct electricity depends on the number of electrons that are able to move . Some of the materials allow current to flow better than others.
What is an Electromotive Force?
If a force acts on electrons to make them move in a particular direction, then up to some extent random motion of the electrons will be eliminated. An overall movement in one direction. The force which acts on the electrons to move them in a certain direction is known as electromotive force and its quantity is known as voltage and is measured in V.