---
title: "Zener current: 15 V, 120 Ω, 360 Ω"
subject: "Basic Electronics Engineering"
chapter: 2
key: "semester_2/basic_electronics_engineering:zener-current-15v-120"
source: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/zener-current-15v-120
site: BCT Engineering
---

# Zener current: 15 V, 120 Ω, 360 Ω

Basic Electronics Engineering · Chapter 2: Diodes

- Asked in: 2069 Bhadra, 3 marks
- Video: [Solved Problems on the Zener Diode](https://www.youtube.com/watch?v=kYtebfx-yHc) — ALL ABOUT ELECTRONICS
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/zener-current-15v-120
- Whole chapter: https://www.bctengineer.com/md/semester_2/basic_electronics_engineering/chapter-2

## Question

Find Iz, assuming Vz = 9 V. [Figure: Vin = 15 V source, series resistor R = 120 Ω, Zener diode Dz in parallel with RL = 360 Ω; output Vout.]

## Short answer

Without the Zener, VL=11.25V > 9V, so the Zener breaks down at 9V. IR = (15-9)/120 = 50mA, IL = 9/360 = 25mA. IZ = IR - IL = 25mA.

## Answer

**Given:** Vin = 15 V, R = 120 Ω, RL = 360 Ω, VZ = 9 V.

Check: without the Zener, VL = 15 × 360/(120 + 360) = 11.25 V, which is greater than 9 V, so the Zener is in breakdown and Vout = 9 V.

- IR = (15 − 9)/120 = 0.05 A = 50 mA
- IL = 9/360 = 25 mA
- IZ = IR − IL = 50 − 25

**Answer: IZ = 25 mA**

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Without the Zener, the voltage across RL is 15 x 360/480. Why does this show the Zener conducts?
   A. 11.25 V is below 9 V
   B. 11.25 V exceeds VZ = 9 V, so breakdown occurs
   C. 360 Ω is larger than 120 Ω
   D. Because the current is 50 mA
   Answer: B. The open-circuit load voltage 11.25 V is above VZ, so the Zener is in breakdown and Vout = 9 V. (Key point: Zener ON check)

2. What is IR?
   A. 25 mA
   B. 75 mA
   C. 125 mA
   D. 50 mA
   Answer: D. IR = (15 - 9)/120 = 50 mA. (Key point: Series current)

3. What is IZ?
   A. 25 mA
   B. 50 mA
   C. 75 mA
   D. 9 mA
   Answer: A. IL = 9/360 = 25 mA, so IZ = 50 - 25 = 25 mA. (Key point: Zener current)

## Related in Basic Electronics Engineering

- [Zener network: VL, IL, Iz, IR](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Azener-regulator-220-ohm) — Basic Electronics Engineering, chapter 2
- [Zener current: 18 V, 100 Ω, RL 1.2 kΩ](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Azener-current-18v-100) — Basic Electronics Engineering, chapter 2, asked 4×
- [Zener current: 16 V, 1 kΩ, RL 3 kΩ](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Azener-current-16v-1k) — Basic Electronics Engineering, chapter 2, asked 4×
- [Clamping circuit output, Vin ±25 V](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Aclamping-25v-10v) — Basic Electronics Engineering, chapter 2
- [Output waveforms of two diode circuits](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Adiode-circuits-output-waveforms) — Basic Electronics Engineering, chapter 2
- [Clipping circuit output, 5 V bias](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Aclipping-circuit-5v-bias) — Basic Electronics Engineering, chapter 2

## Related in other subjects

- [Zener regulator Vo, load effect, minimum RL](https://www.bctengineer.com/question.md?key=semester_3%2Felectronics_devices_and_circuit%3Azener-regulator-6v8-line-load) — Electronics Devices and Circuit, chapter 6, asked 2×
- [Zener with pass transistor: Vo and Iz](https://www.bctengineer.com/question.md?key=semester_3%2Felectronics_devices_and_circuit%3Azener-series-pass-numeric) — Electronics Devices and Circuit, chapter 6
- [Zener regulator output voltage and minimum RL](https://www.bctengineer.com/question.md?key=semester_3%2Felectronics_devices_and_circuit%3Azener-load-regulator-rz-6v8) — Electronics Devices and Circuit, chapter 6
- [Zener circuit output voltage and current](https://www.bctengineer.com/question.md?key=semester_1%2Fbasic_electrical_and_electronics_engineering%3Azener-circuit-120v-5k) — Basic Electrical and Electronics Engineering, chapter 3