## Related questions with answers

Question

A transistor with a height of 0.4 cm and a diameter of 0.6 cm is mounted on a circuit board. The transistor is cooled by air flowing over it with an average heat transfer coefficient of $30W/m^2 \cdot K.$ If the air temperature is $55^\circ C$ and the transistor case temperature is not to exceed $70^\circ C.$ determine the amount of power this transistor can dissipate safely. Disregard any heat transfer from the transistor base.

Solution

VerifiedStep 1

1 of 2The exposed area is

$\begin{align*} A&=\pi DL+\dfrac{\pi}{4}D^2\\ &=\pi*0.6*0.4+\dfrac{\pi}{4}*0.6^2=1.0367\ \text{cm}^2 \end{align*}$

```
The minimum safely heat transfer rate is
```

$\dot{Q}=hA(T_\text{s}-T_\text{air})=30*1.0367*10^{-4}*(70-55)=\color{#c34632}{0.047\ \text{W}}$

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