Thermal Design MCQs

Practice Thermal Design MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 1

Electronic Devices & CircuitsThermal Design

A heat sink attached to a power transistor primarily reduces the thermal resistance from the device toward ambient so that?

AJunction temperature can be kept lower for a given power dissipation
BCurrent gain becomes infinite
CBase current becomes exactly zero
DThe transistor becomes a photodiode

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Correct Answer: A. Junction temperature can be kept lower for a given power dissipation

Explanation: A heat sink improves heat transfer away from the device, lowering junction temperature for a specified dissipated power and ambient condition.

Reference: Standard electronics: transistor heat sinking

Question 2

Electronic Devices & CircuitsThermal Design

A transistor dissipates 2 W. If the total junction-to-ambient thermal resistance is 30 degrees C/W and ambient temperature is 25 degrees C, the estimated junction temperature is?

A55 degrees C
B60 degrees C
C85 degrees C
D115 degrees C

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Correct Answer: C. 85 degrees C

Explanation: Temperature rise is P×theta = 2×30 = 60 degrees C. Adding 25 degrees C ambient gives an estimated junction temperature of 85 degrees C.

Reference: Standard electronics: thermal resistance calculation