Subelement A: RADAR Principles – 10 Key Topics – 10 Exam Questions – 8 Drawings— Topic 10: Circuits-2
Question 8-10A4
Element 8 (RADAR)What is the correct value of RS in Fig. 8A7, if the voltage across the LED is 1.9 Volts with 5 Volts applied and If max equals 40 milliamps?
Explanation
In this series circuit, the resistor (RS) limits the current through the LED to its maximum safe operating level. First, determine the voltage drop across RS. Since the supply voltage is 5 Volts and the LED drops 1.9 Volts, the remaining voltage across RS is 5 V - 1.9 V = 3.1 Volts.
Next, apply Ohm's Law (R = V/I) to find the resistance of RS. The current (I) through RS is the same as the LED's maximum current, which is 40 milliamps (0.040 Amps).
RS = 3.1 Volts / 0.040 Amps = 77.5 Ohms.
The closest answer among the choices is 77 ohms.
Related Questions
8-10A2 If more light strikes the photodiode in Fig. 8A5, there will be:8-10A3 In the circuit shown in Fig. 8A6, which of the following is true?8-10A5 The block diagram of a typical RADAR system microprocessor is shown in Fig. 8A2. Choose the most correct statement regarding this system.8-10A6 You are troubleshooting a component on a printed circuit board in a RADAR system while referencing the Truth Table in Fig. 8A8. What kind of integrated circuit is the component?8-11B1 The magnetron is used to: