Exams › JEE Advanced › Physics

A diode in a circuit has a constant voltage drop of 0.5 V at all currents and a maximum power rating of 100 mW. What should be the value of resistor R (in ohms) connected in series with the diode to obtain maximum current? (Assume the supply voltage is 1.5 V.)

1. 5
2. 6.67
3. 10
4. 20

Correct answer: 5

Solution

The diode operates at a constant 0.5 V. Maximum allowable current: I_max = P_max / V_diode = 0.1 W / 0.5 V = 0.2 A. The remaining voltage appears across R: V_R = V_supply - 0.5 = 1.5 - 0.5 = 1.0 V. For maximum current (I = I_max), R = V_R / I_max = 1.0 / 0.2 = 5 ohms.

Related JEE Advanced Physics questions

• A Zener diode with breakdown voltage Vz = 9 V and maximum power dissipation Pmax = 0.27 W is used to provide a stabilized 9 V supply from a 12 V battery. The Zener is connected in parallel with the load terminals A and B, and a series resistor Rs is placed between the battery and the Zener/load combination. What is the minimum value of Rs that keeps the Zener within its power rating when no load is connected?
• An XNOR logic gate has two inputs A and B. When both A and B are HIGH (logic 1), the output Y1 is obtained. When both A and B are LOW (logic 0), the output Y2 is obtained. What is the pair (Y1, Y2)?
• Which of the following statements about a Light Emitting Diode (LED) are correct? (I) It operates at low voltage and consumes little power. (II) It responds instantly with no warm-up time needed. (III) The bandwidth of emitted light is roughly 100 to 500 angstroms, making it nearly (but not perfectly) monochromatic. (IV) It has a short operational life but is mechanically rugged. (V) It can switch on and off very rapidly.
• A P-N junction diode is isolated (not connected to any external circuit). Which of the following statements about the junction is correct?
• For a logic gate, the output is LOW whenever at least one of its inputs is HIGH. Which gate satisfies this condition?
• In a circuit, a logical value of 1 corresponds to a potential of 3 V at a point, and a logical value of 0 corresponds to 0 V. Point Y gives the output. The truth table of the given circuit is:

⚔️ Practice JEE Advanced Physics free + battle 1v1 →