# Electronic Devices and Circuits Questions and Answers – Diode Resistance

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This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Diode Resistance”.

1. The static resistance R of the diode is given by __________
a) V/I
b) V*I
c) V+I
d) V-I

Explanation: According to Ohms law the electric current in the circuit is directly proportion to voltage and inversely proportional to resistance so, R=V/I.

2. In the volt ampere characteristics of the diode, the slope of the line joining the operating point to the origin at any point is equal to reciprocal of the _________
a) resistance
b) conductance
c) voltage
d) current

Explanation: In the diode’s volt ampere characteristics, the line joining the operating point and the origin, at any point of the line is equal to the conductance so, it is reciprocal of the resistance.

3. At room temperature (VT = 26) what will be the approximate value of r when n=1 and I=100mA?
a) 26 ohms
b) 2.6 ohms
c) 260 ohms
d) 2600 ohms

Explanation: We know that R= (n*VT) /I, by substituting the value of n, VT, I we get R= 260 ohms, (1*26)/100*10-3 = 260 ohms.
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4. In the diode volt ampere characteristics what will be the resistance if a slope is drawn between the voltages 50 to 100 and corresponding current 5 to 10?
a) 5 ohms
b) 10 ohms
c) 50 ohms
d) 100 ohms

Explanation: We know that, in volt ampere characteristics the resistance is equal to the reciprocal of the line joining the origin and operating point, R = dV/dI, by substituting the value of dV and dI we get R= 10ohms.

5. In piecewise linear characteristics what will be the RF value if the slope is 0.5?
a) 25 m ohms
b) 50 m ohms
c) 2 ohms
d) 10 ohms

Explanation: In piecewise linear characteristics the forward resistance will be equal to reciprocal of the slope so, RF = 1/slope, RF = 1/0.5 which is equal to 2 ohms.

6. A diode will behave as an open circuit if the voltage in the circuit is less than __________
a) cut off voltage
b) saturation voltage
c) leakage voltage
d) threshold voltage

Explanation: The diode made up of semiconductor has a certain threshold voltage only after which it behave as closed circuit in the sense it performs some operation if the threshold voltage is greater than the voltage in circuit.

7. What will be the approximate value of thermal voltage of diode?
a) 25mV at 300K
b) 30mV at 180K
c) 25mV at 180K
d) 30mV at 300K

Explanation: We know that the thermal voltage of diode is approximately equal to room temperature which is 300K then for all practical purpose the thermal voltage of diode is taken as 25mV so it will be 25mV at 300K.

8. What will be the thermal voltage of the diode if the temperature is 300K?
a) 25.8 mV
b) 50 mV
c) 50V
d) 19.627 mV

Explanation: The thermal voltage of the diode is given by, VT = KT/q, by substituting the values of T, K which is Boltzmann constant and q which is the charge of the electron we get VT = (300*1.38*10-23)/ (1.602*10-19), VT= 25.8mV.

9. What will be the diode resistance if the current in the circuit is zero?
a) 0 ohms
b) 0.7 ohms
c) 0.3 ohms
d) 1 ohms

Explanation: When the current in the circuit is zero there will be no flow of charges to resist hence the diode resistance will be zero.

10. Which of these following is not a characteristic of an ideal diode?
a) Perfect conductor when forward bias
b) Zero voltage across it when forward bias
c) Perfect insulator when reverse bias
d) Zero current through it when forward bias

Explanation: The diode acts as an ideal diode when it is a perfect conductor and has zero voltage across it during forward bias, a perfect insulator and zero current through it during reverse bias.

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.

To practice all areas of Electronic Devices and Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers. 