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Online MCQ Assignment
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1. Which of the following heat sink is used for low power application
a) Stamped heat sink
b) Machining heat sink
c) Aluminum heat sink
d) Bolded-Fin heat sink

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Answer: a [Reason:] Stamped heat sinks are made of metal that are stamped to form a particular shape. These are cheaper compared to extruded heat sinks. These are used for low-power applications and hence these are low in performance.

2. The performance of heat sink does not depend upon
a) Choice of material
b) Protrusion design
c) Surface treatment
d) none of the mentioned

View Answer

Answer: d [Reason:] The performance of the heat sink depends on the factors like the choice of a material, protrusion design, surface treatment and air velocity.

3. Heat sinks are also called
a) High sinks
b) Heat spreaders
c) On-sinks
d) Active heat sinks

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Answer: b [Reason:] Heat sinks are also called as Heat spreaders, which are frequently used as covers on a computer’s memory to dissipate its heat.

4. Heat dissipation from heat sink take place primarily by
a) Conduction
b) Convection
c) Radiation
d) All of the mentioned

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Answer: d [Reason:] Heat dissipation from heat sink take place primarily by convection since there is no actual contact between heat sink and transistor. Heat dissipation is also take place by Radiation but it is comparatively low.

5. Heat sinks are provided with peripheral fins to
a) Provide good appearance
b) Increase heat absorption
c) Increase surface area of heat dissipation
d) Provide material stability

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Answer: c [Reason:] Heat sinks are provided with peripheral fins to increase surface area of heat conduction. Increase in dissipation also increase absorption but more correct option is c.

6. Heat sinks are usually provided with black anodized finish to
a) Enhance heat dissipation by radiation
b) Enhance heat dissipation by convection
c) Prevent electrical connection
d) Remove dust accumulation

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Answer: a [Reason:] Heat sinks are usually provided with black anodized finish to enhance heat dissipation by radiation.

7. Which substance is used to maintain electrical insulation between heat sink and transistor?
a) plastic
b) fiber
c) ceramic
d) mica

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Answer: d [Reason:] Substance is used to maintain electrical insulation between heat sink and transistor is a mica layer.

8. De-rating factor is usually expressed in
a) W/°C
b) °C/W
c) W/s
d) kW/K

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Answer: a [Reason:] De-rating factors for determining the power dissipation rating is usually given at any temperature above 25°C. The de-rating factor is specified in W/°C.

9. Cavities embedded in heat source is also known as
a) Low sink
b) Sink hole
c) On-sink
d) Inverted sink

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Answer: d [Reason:] Cavities embedded in heat source is also known as inverted sink.

10. By dividing volumetric thermal resistance by required thermal resistance we will obtain
a) Power dissipation of heat sink
b) Volume of heat sink
c) Maximum temperature of heat sink
d) Volume of surrounding air

View Answer

Answer: b [Reason:] By dividing volumetric thermal resistance by required thermal resistance we will obtain volume of heat sink.