Question

15. You are given a 400v 800W device.
a) What is its power at 200V?
b) What if 600V is applied?
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Answer 1

Given:

A device with 400 V/800 W rating

To find:

• Power dissipation at 200 V
• What would happen if 600 V is applied ?

Calculation:

• Let resistance of device be R :

$R = \dfrac{{voltage}^{2} }{power}$

$\implies R = \dfrac{{400}^{2} }{800}$

$\implies R = 200 \: ohm$

Now, power dissipation at 200 Volt is :

$\boxed{P = \dfrac{ {200}^{2} }{200} = 200 \: watt}$

• Since the max rating of the device is at 400 volts, if we apply a potential difference of 600 volts, the device may burn out.